V 


CONCRETE 


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^PuiUSHBlTtBY  THE 


i 


Chicago  ’— t^PitTSBURo' 


I  Vo  -  I 


UNIVERSAL  PORTLAND  CEMENT  CO. 


REINFORCED  CONCRETE  POLES. 

By  R.  D.  Coombs, 

M.  Am.  Soc.  C.  E., 

AND  C.  L.  Slocum, 

Asso.  M.  Am.  Soc.  C.  E. 


The  increasing  demands  of  the  telephone,  telegraph,  light,  and 
power  companies,  and  the  wide  development  of  electric  traction, 
together  with  the  increased  scarcity  and  cost  of  good  timber  poles, 
has  compelled  engineers  to  look  for  a  suitable  substitute  possessing 
the  desirable  qualities  of  wooden  poles,  but  without  the  necessity 
of  continual  maintenance  and  frequent  renewals. 

According  to  a  report  of  the  Forest  Service,  United  States  De¬ 
partment  of  Agriculture,  the  telegraph  and  telephone  companies 
purchase  about  two-thirds  of  the  total  number  of  timber  poles  used 
each  year.  The  remainder  may  be  credited  to  the  steam  and  electric 
railroads,  and  the  electric  light  and  power  companies.  The  total 
number  of  timber  poles  over  20  feet  in  length  purchased  in  1906 
was  reported  as  3,574,666,  and  their  value,  at  the  point  of  purchase, 
as  $9,471,171,  or  an  average  of  $2.65  per  pole.  In  Table  1  are  shown 
the  number  and  average  value,  at  the  point  of  purchase,  for  varying 
lengths  of  the  five  leading  varieties  of  timber.  Other  varieties,  and 
the  sawed  poles  of  the  varieties  given,  are  omitted  from  the  table, 
since  their  combined  number  is  relatively  small. 

By  far  the  greater  number  of  poles  are  cedar  and  chestnut,  and, 
as  the  former  grow  in  the  Lake  States,  Maine,  northern  New  York, 
and  Idaho,  and  the  latter  in  Pennsylvania,  Maryland,  Virginia,  and 
West  Virginia,  the  item  of  freight  to  be  added  to  the  tabular  value 
may  be  a  considerable  factor  of  the  final  cost.  The  rapid  increase  in 
the  cost  of  timber,  which,  as  shown  by  Table  I,  is  still  further  in¬ 
creased  for  long  lengths,  and  the  deterioration  of  unpreserved  timber, 
have  forced  purchasers  to  consider  the  use  of  other  methods  and 
materials. 

[Copyright,  1910,  by  Association  of  American  Portland  Cement  Manufacturers.] 


REINFORCED  CONCRETE  POLES 


TABLE  1.— ROUND  POLES  (1906).* 


Length 

20  TO  25  Feet. 

Length  26 
TO  30  Feet. 

Length  31 
TO  35  Feet. 

Length  36 
TO  40  Feet. 

Length  41 
Feet  and 
Over. 

Totals. 

Number. 

Average 

Value. 

Num¬ 

ber, 

Average 

Value. 

Num¬ 

ber. 

Average 

Value. 

Num¬ 

ber. 

Average 

Value. 

Num¬ 

ber. 

Average 

Value. 

Num¬ 

ber. 

Average 

Value. 

Cedar  .  .  . 

1,305,148 

$1.19 

408,139 

$3.22 

262,739 

$4.94 

123,391 

$6.17 

70,452 

$9.08 

2,169,869 

$2.57 

Chestnut . 

404,877 

$1 .42 

265,315 

$2.52 

184,028 

$3.35 

75,108 

$4.64 

.57,975 

$7.08 

987,303 

$2.65 

Pine . 

77,730 

$1.68 

30,520 

$3.18 

25,914 

$4.84 

15,828 

$5.13 

12,609 

$12.41 

162,601 

$3.63 

Cypress  . 

27,041 

$1.09 

40,263 

$1.24 

22,700 

$3.04 

14,101 

$4.42 

7,187 

$6.28 

111,292 

$2.30 

Juniper  . . 

24,063 

$1.62 

12,003 

$2.70 

10,638 

$3.68 

4,113 

$4.09 

6,247 

$5.76 

57,064 

$2.86 

Totals  . 

1,838,859 

$1.27 

756,240 

$2.86 

506,019 

$4.24 

232,541 

$5.50 

154,470 

$8.33 

3,488,129 

$2.60 

In  its  function  as  a  carrier  of  wires  a  pole  resists  downward, 
lateral,  and,  to  some  degree,  torsional  forces.  A  little  strength 
against  compression,  a  superior  resiliency,  and  a  long  life  in  a  variable 
climate  and  soil,  are  the  chief  requirements  of  a  good  pole. 

Until  recently  wooden  poles  have  been  so  cheap  that  the  ad¬ 
visability  of  using  a  wood  preservative  to  delay  decay  has  not  been 
widely  or  seriously  considered,  and  because  the  expense  of  treating 
the  entire  pole  exceeded  the  additional  benefit  or  life  attained.  In 
addition,  many  poles  have  to  be  renewed  not  only  on  account  of 
decay,  but  because  poles  of  larger  capacity  are  required.  The  future 
demands  upon  an  installation  cannot  always  be  foretold  with  ac¬ 
curacy.  The  duration  of  the  useful  life  of  a  timber  pole,  in  contact 
with  the  soil,  depends  in  part  upon  the  chemical  action  of  the  in¬ 
gredients  of  the  earth  and  upon  its  ability  to  resist  local  insect  life. 
Disintegration  will,  therefore,  advance  more  rapidly  in  some  soils 
than  in  others,  but  in  general  the  use  of  native  timber  for  local  use 
will  be  found  advisable.  The  zone  of  decay  at  the  ground-line  is 
produced  by  alternate  wetting  and  drying,  inducing  a  condition  of 
decay  which  frays  away  the  body  of  the  pole  until  this  critical 
section  is  so  emaciated  that  it  will  no  longer  sustain  its  load.  In 
the  dry  season  this  decayed  portion  is  much  in  the  nature  of  dry 
tinder,  and  if  the  pole  is  located  on  a  grassy  right  of  way,  grass  fires 
char  away  still  more  of  the  critical  section.  An  application  of  coal- 
tar  to  this  portion  of  the  pole,  while  proper  in  desert  localities,  would 
promote  the  early  destruction  of  the  pole  in  places  subject  to  running 
grass  fires. 

Preservative  treatment  and  the  consequent  use  of  inferior  grades 
of  timber  will  no  doubt  afford  temporary  relief,  but  it  is  entirely 

*  United  States  Forest  Service,  Circular  No.  137. 

2 


UNIVERSAL  PORTLAND  CEMENT  CO. 


probable  that  within  the  next  decade  some  form  of  artificial  pole 
will  be  able  to  compete  in  first  cost  with  the  wooden  poles  then 
available.  In  case  it  is  necessary  to  use  long,  heavy  poles,  or  if  the 
character  of  line  is  such  that  safety  and  permanence  are  prime  re¬ 
quisites,  it  will  frequently  be  economical  to  use  reinforced  concrete 
poles. 

In  addition  to  the  timber  poles  there  are  used  each  year  a  rela¬ 
tively  small  though  increasing  number  of  metal  poles.  Steel  poles 
or  towers  are  coming  into  more  general  use  for  power  transmission 
lines,  particularly  as  applied  to  long  spans  or  high  poles.  Until 
recently  such  steel  towers  have  been  built  of  the  lightest  sections, 
often  from  }  s  fo  M  i^^ch  in  thickness,  and  thus  requiring  great  care 
in  handling  and  frequent  painting.  As  a  rule,  structures  exposed 
to  the  elements  are  not  given  frequent  attention,  and  are  only  re¬ 
painted  after  oxidation  has  occurred  to  a  marked  extent. 

During  the  last  few  years  steel  transmission  line  poles  of  substan¬ 
tial  construction,  using  sections  whose  thickness  and  length  ratios 
are  in  accord  with  the  best  modern  practice,  have  been  built  by 
several  of  the  large  eastern  railroads.  Some  of  the  lines  referred  to 
carry  a  large  number  of  heavy  wires,  and  for  this  and  other  reasons 
were  not  well  adapted  to  the  use  of  wooden  poles. 

Since  steel  is  comparatively  expensive  and  requires  maintenance 
to  prevent  corrosion,  considerable  attention  has  been  given  to  the 
use  of  reinforced  concrete  poles  for  both  telegraph  and  transmission 
line  construction. 

When  steel  is  embedded  in  well-made  concrete  its  preservation  is 
perfect,  and  the  life  of  a  reinforced  monolith  is  practically  indefinite. 
If  designed  and  built  with  the  same  attention  now  given  other  mate¬ 
rials,  reinforced  concrete  poles  should  attain  the  necessary  strength 
and  give  satisfactory  service.  As  in  the  case  of  steel  poles,  they  can 
be  spaced  greater  distances  apart  than  is  economically  possible  with 
wooden  poles,  and  in  their  fire-resisting  qualities  are  at  least  equal 
to  steel  poles.  This  latter  feature  will  become  of  increased  im¬ 
portance  with  the  spread  of  modern  requirements  for  fire  protection. 

Concrete  poles  are  of  a  pleasing  gray  color  and  are  readily  modified 
in  outline,  or  in  the  treatment  of  the  base,  to  suit  the  locality  in  which 
they  may  be  situated. 

By  the  insertion  of  pipes,  or  the  formation  of  an  axial  passage  in 
the  concrete,  wires  may  be  carried  from  the  pole  tops  to  the  ground, 
and  thence  in  any  desired  direction,  and  are  thus  entirely  protected 
at  little  additional  cost. 


3 


REINFORCED  CONCRETE  POLES 


In  damp  climates,  or  in  localities  where  wooden  poles  are  subject 
to  attack  by  fungi,  or  insects,  concrete  poles  have  a  longer  life  than 
either  steel  or  timber. 

On  long  or  important  transmission  lines  where  reliability  of  service 
is  of  great  value,  it  may  be  conceded  that  the  additional  expense  of  a 
material  superior  to  timber  will  often  be  warranted. 

Owing  to  the  natural  taper  of  the  timber,  it  is  frequently  the 
case  that  the  weakest  section  of  a  timber  pole  is  at  some  point  above 
the  ground  level.  Therefore  there  is  an  excess  of  material  in  the 
butt,  which  may  be  considered  wasted,  except  in  so  far  as  this  surplus 
timber  is  useful  in  resisting  decay.  A  reinforced  concrete  pole  may 
be  given  any  desired  taper  and  need  have  no  excess  of  improperly 
placed  material. 

The  character  of  service  required  of  line  poles  is  not  that  of  a 
column,  as  might  at  first  be  supposed,  but  of  a  cantilever  beam. 
Further,  in  order  to  reduce  the  stresses  in  the  pole  under  certain  con¬ 
ditions  of  loading,  it  becomes  necessary  for  the  pole  to  deflect  in  the 
direction  of  the  line,  and  therefore  a  certain  elasticity  is  desirable 
in  the  material. 

If  we  may  judge  by  the  kind  of  handling  which  concrete  piles 
successfully  withstand,  it  would  seem  entirely  probable  that  concrete 
poles  will  survive  any  shocks  incident  to  ordinary  service.  When 
subjected  to  an  overload  or  accidental  shock,  a  timber  pole  will  bend 
and  in  some  cases  survive;  but  failure,  when  it  does  occur,  is  usually 
complete,  and  the  pole  falls.  Concrete  poles,  on  the  contrary,  while 
without  the  elasticity  of  timber,  do  not  fail  by  breaking  off,  but  are 
held  by  the  reinforcement  from  falling  to  the  ground.  Tests  also 
show  that  a  reasonable  amount  of  bending  (sufficient  for  the  balanc¬ 
ing  of  stresses  in  the  wires)  can  occur  without  apparent  injury  to  the 
pole. 

The  chief  cause  of  skepticism  heretofore  has  been  the  fear  that 
such  long,  slender  members  would  not  be  able  to  withstand,  without 
cracking,  the  bending  stresses  and  measurable  deflections  of  a  pole 
line.  If  the  poles  are  properly  designed,  cracks  due  to  partial  failure 
will  not  occur.  Hair  cracks  are  of  infrequent  occurrence,  micro¬ 
scopic  in  character,  and  experience  has  shown  that  they  will  not 
admit  moisture  in  sufficient  quantity  to  injure  a  reinforced  concrete 
structure. 

In  view  of  the  various  successful  installations  in  this  country 
and  in  Europe,  and  assuming  that  proper  unit  stresses  are  used  in 
designing,  and  the  necessary  care  taken  to  obtain  a  dense  mixture 

4 


UNIVERSAL  PORTLAND  CEMENT  CO. 


and  a  good  surface  finish,  the  writers  do  not  believe  that  there  need 
be  any  apprehension  of  injury  due  to  cracks. 

The  location  of  pole  lines  is  not  always  well  adapted  to  the  con¬ 
venient  transportation  of  materials,  and,  as  the  erection  of  such  lines 
is  frequently  done  by  hand  or  with  light  rigging,  it  is  not  desirable 
that  poles  should  be  of  great  weight.  The  greater  weight  of  concrete 
poles,  rendering  their  shipment  a  matter  of  increased  expense,  as 
compared  with  timber,  and  the  possibility  of  injury  in  handling  to  the 
site,  introduces  a  question  as  to  the  relative  advantage  of  manufacture 
at  the  site  or  at  distant  yards.  In  many  cases  it  will  be  found  ad¬ 
vantageous  to  manufacture  poles  at  one  or  more  favorably  located 
points  in  order  to  avoid  the  transportation  of  raw  materials,  forms, 
housing,  men,  water,  etc.,  and  because  it  is  not  always  possible  to 
obtain  space  for  manufacture  immediately  adjacent  to  the  site.  On 
the  other  hand,  certain  conditions  of  inaccessibility  will  make  it 
desirable  to  haul  raw  materials  to  the  site,  rather  than  to  attempt 
the  more  difficult  handling  of  long  monolithic  poles.  The  investiga¬ 
tion  reduces  to  the  availability  of  the  material  for  the  service  re¬ 
quired  and  the  relative  cost.  The  matter  of  cost  is  complicated  by 
the  locality  of  manufacture  and  the  cost  of  erection,  so  that  at  the 
present  time  each  installation  must  be  judged  separately,  and  the 
real  question  at  issue  is  one  of  availability.  It  may  be  noted  in 
passing  that,  in  a  number  of  instances,  reinforced  concrete  poles 
have  been  installed  at  a  lower  cost  than  steel  or  wood. 

History  of  the  Development  of  Concrete  Poles. 

The  earliest  concrete  poles  in  America  were  designed  and  erected 
on  the  Isthmus  of  Panama  by  Col.  G.  M.  Totten,  Chief  Engineer 
of  the  Panama  Railroad  Company,  about  1856.  Concrete  was 
used  on  account  of  the  ravages  of  insects.  These  poles  were  about 
12  feet  long,  circular  in  section,  having  a  6-  to  8-inch  top  and  12-  to 
15-inch  base.  The  wires  were  carried  on  iron  bracket  cross-arms, 
fastened  to  the  tops  of  the  poles  by  wrought-iron  bands.  The  pro¬ 
portions  of  the  concrete  are  not  now  obtainable.  The  first  poles  were 
entirely  of  concrete,  but  since  they  were  not  capable  of  withstanding 
lateral  strains,  they  were  replaced  by  poles  reinforced  with  a  3  by 
3-inch  wooden  core.  This  latter  construction  was  also  a  failure, 
because  the  wooden  cores  swelled  and  cracked  the  concrete,  and  both 
types  of  poles  were  abandoned,  so  that,  in  1888,  there  were  only  about 
twenty  of  the  original  installation  standing. 

5 


REINFORCED  CONCRETE  POLES 


About  1900  the  practice  of  using  concrete  bases  around  the  de¬ 
cayed  butts  of  wooden  poles  became  quite  common.  It  is  alleged 
that  these  poles  are  better  than  new  ones,  and  that  a  saving  of  35  to 
55  per  cent,  is  made  by  their  use  in  reconstruction. 

The  first  use  of  reinforced  concrete  poles  in  Europe  is  perhaps  un¬ 
certain,  but  a  French  engineer,  M.  Hennebique,  was  probably  the 
originator  of  this  form  of  construction.  The  trolley  poles  built  by 
him  in  1896,  for  the  Le  Mans  Tramway  Company,  in  France,  are  in 
use  to-day.  These  poles  are  solid,  circular  in  section,  and  reinforced 
with  small  round  rods  and  transverse  wires. 

In  1900,  M  Porcheddu  made  the  test  given  below,  upon  a  Henne¬ 
bique  pole,  for  the  Societa  Anomina  di  Elettricita  Alba  Italia,  of 
Bologne,  Italy.  Some  of  these  poles  are  in  use  in  a  tramway  line 
between  Borgone  and  Russoleno.  They  are  about  35  feet  long, 
having  a  15-inch  base  and  a  7-inch  top,  and  are  of  solid  square  cross- 
section.  Small  round  rods  were  used  as  reinforcement. 


Diameter  at  top . 6.3  inches 

Diameter  at  bottom . 13.8  inches 

Total  length  of  pole . 35.0  feet 

Length  above  ground . 29.5  feet 

Distance  of  load  above  ground . 27.7  feet 

Distance  of  load  above  point  of  failure .  7.0  feet 


In  Table  2  are  given  the  elastic  and  also  the  permanent  deforma¬ 
tions  for  increasing  test  loads;  the  point  of  application  of  the  load 
being  about  one  foot  below  the  top  of  the  pole. 


TABLE  2. 

Pull  in  Pounds. 

Deformation  in  Inches. 

Permanent  Deformation. 

463 

1.06 

0.00 

926 

3.34 

0.00 

1300 

5.50 

0.71 

1521 

7.27 

0.71 

1962 

10.61 

0.71 

2182 

14.34 

1.57 

2205 

14.93 

2.75 

2866 

15.33 

2.75 

4012 

28.30 

2.75 

4410 

Bupture. 

Fig.  1  represents  graphically  the  behavior  of  this  pole  under 
various  loads. 

M.  Porcheddu  also  tested  a  design  of  his  own,  and  a  number  of 
poles  of  this  type  were  afterward  placed  in  a  tramway  line.  This  pole 

6 


UNIVERSAL  PORTLAND  CEMENT  CO. 


was  about  35  feet  in  length,  square  in  cross-section,  7  inches  at  the 
top  and  15  inches  at  the  bottom,  solid,  and  reinforced  with  small 
smooth  rods.  A  pull  of  4000  pounds,  at  the  top,  gave  a  maximum 


Fig.  1. 
7 


REINFORCED  CONCRETE  POLES 


deflection  of  2  feet  6  inches,  the  pole  returning  to  within  3  inches  of 
the  normal  position.  This  pole  safely  withstood  4500  pounds  and 

broke  at  4700  pounds,  but  was  held  by  its 
reinforcement  from  falling  to  the  ground. 
On  a  high-tension  transmission  line  be¬ 
tween  Li  vet  and  Grenoble,  a  distance  of 
about  20  miles,  M.  A.  Burgeat  installed 
the  combination  poles  shown  in  Fig.  2.  In 
the  manufacture  of  these  poles  wooden 
poles  were  thoroughly  dried,  cleaned,  and 
trimmed,  reducing  the  diameter  about  1 
inch  in  every  7  feet.  In  a  stiff  cement 
paste  covering  this  wooden  core,  yVii^ch 
round  rods  were  wound  in  a  spiral.  Tied 
to  this  spiral  and  placed  longitudinally 
were  round  rods  of  yV"  lo  |-inch  diam¬ 
eter,  the  cross-section,  number,  and  area 
of  the  rods  depending  upon  the  length  and 
strength  of  the  poles  desired.  The  concrete 
covering  was  applied  by  placing  the  steel-encased  wooden  core  in  a 
form  and  pouring  concrete  around  it.  These  poles,  while  strong, 
were  cumbersome,  almost  as  heavy  as  solid  concrete,  and  required 
considerable  time  to  manufac¬ 
ture.  In  addition,  a  wooden 
core  is  subject  to  organic  change, 
and  may  cause  cracks  in  the  con¬ 
crete,  by  expansion  or  contrac¬ 
tion,  as  its  moisture  content 
varies. 

A  more  recent  process  in¬ 
vented  by  the  German  firm  of 
Otto  &  Schlosser,  at  Meissen,  on 
the  Elbe,  consists  in  manufac¬ 
turing  poles  in  revolving  forms 
by  centrifugal  force.  A  few  of 
these  poles  have  been  installed 
on  the  government  telegraph 
lines  in  Meissen,  and  it  is  stated 
that  thus  far  they  have  not  required  any  maintenance  expendi¬ 
tures.  To  a  wet  mixture  of  rich  concrete  is  added  finely  ground 
asbestos  fiber,  and  the  resulting  mixture  is  placed  in  a  tubular  form, 

8 


UNIVERSAL  PORTLAND  CEMENT  CO 


inside  which  the  reinforcement  of  expanded  metal  has  been  fastened, 
and  revolved  at  high  speed.  It  is  claimed  that  the  centrifugal  action 
forces  the  concrete  to  an  even  thickness  against  the  reinforcement, 
the  operation  taking  place  in  a  warm  room  and  occupying  but  a 
few  minutes.  By  the  addition  of  asbestos  fiber  the  strength  of  the 
poles  in  tension  is  said  to  be  increased.*  These  hollow  poles,  shown  in 
cross-section  (Fig.  3) ,  have  the  butts  filled  with  stones  to  the  ground-line. 

The  Brescia  Construction  Company,  of  Brescia,  Italy,  have 
constructed  a  novel  kind  of  pole,  in  lengths  from  26  to  33  feet,  and 
of  ordinary  telegraph,  telephone,  or  trolley  capacity.  The  form  of 
construction  is  shown  in  Fig.  4;  a  large  round  bar  in  each  of  the  three 
corners,  firmly  cross-tied,  composes  the  reinforcement.  The  poles 
are  cast  in  wooden  forms  and  are  tapered.  The  manufacturers  of 
this  pole  claim  that  their  product  is  cheaper  than  corresponding  iron 
poles.  These  poles  are  unclimbable  without 
a  special  attachment,  which  is  supplied  to 
the  workmen. 

Perhaps  the  most  remarkable  process  of 
foreign  pole  manufacture,  known  as  the  Swiss 
process,  is  that  invented  and  controlled  by 
the  Messrs.  Siegwart.  This  embodies  a  new 
idea  in  pole  manufacture,  and  is  a  strong 
indication  that  an  economical  concrete  pole 
will  eventually  be  evolved  to  successfully 
compete,  in  point  of  first  cost,  with  the  common  forms  in  wood  and  iron. 
The  Siegwart  process  consists  essentially  of  a  horizontal,  collapsible  core 
of  sheet-iron,  with  pivoted  ends,  carried  by  a  movable  frame  which  is 
provided  with  trucks.  Below  this  revolving  core  is  a  frame  supporting 
the  continuous  conveyor  belt,  which  receives,  distributes,  and  applies 
the  concrete  to  the  fabricated  steel  skeleton,  when  the  latter  has  been 
fastened  in  the  revolving  core.  The  reinforcement  consists  of  small 
rods  arranged  lengthwise  and  held  accurately  in  place  by  adjustable 
rings,  with  grooves  to  keep  the  steel  evenly  spaced  and  at  the  proper 
distance  from  the  interior  and  exterior  concrete  surfaces.  On  the 
under  frame  is  mounted  an  electric  motor  which  operates  the  moving 
parts  by  means  of  belts  and  worm  gearing.  The  conveyor  belt  of 
heavy  wire  netting  is  flat,  and  by  a  system  of  weights  is  kept  con¬ 
stantly  taut,  so  that  during  a  complete  forward  revolution  of  the 

*  The  writers  question  whether  much  benefit  can  be  derived  by  the  addition 
of  asbestos  fiber,  and  in  view  of  the  experiments  by  L.  S.  Moisseiff  (Am.  Soc. 
Test.  Mat.,  1909)  would  prefer  wire  scrap. 

9 


REINFORCED  CONCRETE  POLES 


Fig.  5. — Siegwart  hollow  reinforced  concrete  poles, 


UNIVERSAL  PORTLAND  CEMENT  CO. 


Fig.  6,  Fig.  7. 

Siegwart  hollo v/  reinforced  concrete  poles. 

11 


REINFORCED  CONCRETE  POLES 


core  the  concrete  is  applied  or  wrapped  spirally  around  the  core  under 
pressure,  one  lap  at  a  time,  after  which  another  batch  is  fed  upon  the 
belt  and  the  core  automatically  moves  forward.  The  under  frame 
also  carries  a  small  mixer  which  supplies  the  concrete  simultaneously 
with  the  other  movements.  The  concrete  is  of  a  dry  consistency  of 
Portland  cement,  sand,  and  screenings,  and  as  rapidly  as  applied  is 
bound  fast  by  canvas,  wound  around  and  smoothed  out  by  pressing 
rollers  which  take  up  the  slack  in  the  canvas  binding  by  a  special 
contrivance.  When  the  core  has  traveled  the  full  length  of  the  pole, 
it  is  entirely  covered  with  concrete  and  canvas.  The  pole  is  allowed 


Fig.  8. — Hollow  concrete  poles  made  by  the  Siegwart  process. 


to  cure  in  a  horizontal  position,  from  ten  to  fifteen  hours,  after  which 
the  steel  core  is  collapsed  and  withdrawn.  In  about  seven  days, 
when  the  concrete  has  sufficiently  hardened,  its  canvas  cover  is 
removed  and  the  pole  is  ready  for  the  cross-arms  and  cap.  Poles 
of  different  lengths,  thickness  of  shell,  arrangement  and  weight  of 
reinforcement,  can  be  made  according  to  the  strength  required. 
This  system  has  produced  poles  up  to  45  feet  in  length,  consuming 
about  an  hour  in  the  operation.  The  poles  cost  a  little  more  than 
wooden  poles,  but  less  than  iron  ones,  and  their  light  weight  facili¬ 
tates  handling  and  reduces  freight  charges.  They  present  a  good  ap¬ 
pearance,  with  perfectly  straight  lines,  and  are  tapered  or  fitted 

12 


UNIVERSAL  PORTLAND  CEMENT  CO. 


with  artistic  bases  to  conform  aesthetically  with  their  surroundings. 
The  great  advantage  of  these  poles  is  that  they  can  be  made  by 
machinery  in  any  size  and  quantity. 

A  large  number  were  used  on  the  transmission  line  of  the  elevated 
works  at  Rathausen  near  Luzerne,  the  Olten-Aarburg  electrical 
works,  and  the  central  station  of  the  town  of  Zurich.  These  poles 
withstood  a  heavy  snow-storm  in  Switzerland,  in  May,  1908,  which 
destroyed  a  large  number  of  wooden  poles.  The  internal  and  ex¬ 
ternal  appearance  of  this  pole  is  shown  in  Figs.  5,  6,  7,  8,  and  9. 

In  1903  Robert  Cummings,  M.  Am.  Soc.  C.  E.,  constructed  some 
experimental  concrete  telegraph  poles  at 
Hampton,  Va.  These  poles  were  about  30 
feet  long,  with  the  cross-section  of  an  equi¬ 
lateral  triangle  having  12-inch  sides  and  re¬ 
inforced  with  ^-inch  rods  in  the  corners. 

Hunter  McDonald,  Chief  Engineer  of  the 
Nashville,  Chattanooga  and  St.  Louis  Rail¬ 
way,  has  had  in  use  for  some  four  and  one- 
half  years  a  reinforced  concrete  support  for  a 
standard  bridge  warning  (Fig.  10).  Some  of 
the  first  supports  were  molded  complete  with 
pole,  brace,  and  cross-arm,  of  concrete.  The 
arm  and  brace  were  found  to  be  too  expensive, 
so  these  parts  were  afterward  made  of  pipe. 

One  of  the  poles,  with  concrete  arms  and 
braces,  after  four  and  one-half  years^  service, 
shows  considerable  bending,  but  the  com¬ 
posite  pole  remains  erect.  For  the  shaft  ^  cubic  yard  of  platform 
screenings,  34  cubic  yard  of  sand,  and  234  bags  of  Portland  cement 
were  used.  The  base  consists  of  134  cubic  yards  of  stone,  ^  cubic 
yard  sand,  and  6  bags  of  cement. 

Early  in  1904  the  United  Traction  Company  of  Albany,  N.  Y., 
began  a  series  of  experiments  on  reinforced  concrete  poles  by  first 
testing  a  model  pole  (Figs.  11  and  12).* 

*  Abstracted  from  data  prepared  by  C.  T.  Middlebrook,  M.  Am.  Soc.  C.  E., 
Albany,  N.  Y. 

Length  from  wall  to  load . —  6'  0" 

Cross-section  at  wall .  =  4"  x  4" 

Cross-section  at  load . . . =  23^"  x  23^2^^ 

Maximum  longitudinal  steel  . =4.7%  of  section  at  wall 

Maximum  longitudinal  steel  (intension)  =  1.78%  of  section  at  wall 
Concrete  a  wet  mixture  of  1 :  4  Portland  cement  and  unscreened 
limestone. 

Age  at  test 


Fig.  9. — Siegwart  pole. 


13 


=  6  weeks. 


REINFORCED  CONCRETE  POEES 


14 


UNIVERSAL  PORTLAND  CEMENT  CO. 


Fig.  11.-  Model  test  pole.  United  Traction  Co. 


REINFORCED  CONCRETE  POLES 


The  reinforcement  was  composed  of  twelve  square,  cold 

twisted,  steel  bars,  four  extending  the  full  length,  four  to  the  three- 
quarter  point,  four  to  the  middle  of  the  pole,  and  all  held  firmly 
together  by  a  double  coil  of  No.  12  wire  with  a  2-inch  pitch. 

TABLE  3. 


Load  (Lbs.). 

Deflection 

(Inches). 

Bending 

Moment* 

(Inch-lbs.). 

200 . 

% 

14,400 

300 . 

13^ 

21,600 

400 . 

28,800 

550 . 

31^ 

39,600 

600 . 

43,200 

700 . 

43^2-12 

50,400 

Unit  Tension 
IN  Steel* 
(Lbs.  Per 

Sq.  In.). 

Unit  Comp. 

IN  Steel* 
(Lbs.  Per 
Sq.  In.). 

Unit  Comp. 
IN  Concrete* 
(Lbs.  Per 
Sq.  In.). 

19,200 

8,200 

840 

28,800 

12,300 

1270 

38,400 

16,400 

1690 

52,800 

22,600 

2320 

57,600 

24,600 

2530t 

67,200 

28,800 

2960t 

At  failure  the  reinforcement  exerted  considerable  resistance  to 
compression,  after  the  outer  coating  of  concrete  had  been  crushed- 
The  high-unit  stresses  are  undoubtedly  due  to  the  size  of  the  spec¬ 
imen,  the  efficient  webbing,  and  the  unit  cage  construction. 

In  consequence  of  the  favorable  showing  of  this  model,  a  pole 
suitable  for  electric  railway  service  was  then  made,  having  the  follow¬ 
ing  characteristics: 


Length  above  ground . . =  28  ft. 

Length  below  ground . =  6  ft. 

Cross-section  at  base . =  13"  x  13" 

Cross-section  at  ground . =12"xl2" 

Cross-section  at  top . =  8"  x  8" 

Maximum  longitudinal  steel . =  2.5%  of  section 

Maximum  longitudinal  steel  (in  tension) . =  1.76%  of  section 

Concrete,  a  wet  mixture  of  1  :  4  Portland  cement  and  crusher  run 
limestone,  the  maximum  diameter  of  the  stone  being  Y2  inch. 
Age  at  test . =6  weeks. 


The  reinforcement  was  composed  of  ten  and  two  ^-inch 

square  cold  twisted  steel  bars,  eight  of  which  were  arranged  in  a 
circle  and  enclosed  in  a  spiral  of  twisted  steel  with  a  6-inch 

pitch.  Two  ^-inch  and  two  J^-inch  rods  were  symmetrically  placed 
in  the  corners  outside  the  circle  and  extended  the  full  length  of  the 
pole;  the  remaining  rods  terminated  in  groups  at  the  one-half  and 
three-quarter  points. 

*  Computed  for  comparison  by  the  authors, 
t  Small  cracks  3  to  6  inches  long  appeared  on  the  tension  side, 
t  Progressive  failure  by  extension  of  steel  and  crushing  of  concrete  at  sup¬ 
port.  On  the  removal  of  250  pounds  the  pole  recovered  several  inches  of  the 
12-inch  deflection. 


16 


UNIVERSAL  PORTLAND  CEMENT  CO 


Fig.  13. — Test  pole  built  by  United  Traction  Co.,  of  Albany,  N.  Y. 


2 


17 


REINFORCED  CONCRETE  POLES 


This  pole  was  designed  for  a  pull  of  1000  pounds  applied  20  feet 
from  the  ground,  but,  as  can  be  seen  from  Fig.  13,  is  not  apparently 
subjected  to  any  considerable  loading.  It  is  now  five  years  old  and 
reported  to  be  in  as  good  condition  as  when  erected,  with  no  evidences 
of  injury,  except  a  few  hair  cracks,  due  to  an  excess  of  fine  material, 
or  to  having  been  cast  in  a  heated  atmosphere.  Its  chief  interest 
is  in  that  it  is  believed  to  be  one  of  the  first,  if  not  the  first,  reinforced 
concrete  pole  erected  in  the  United  States,  for  electric  railway  or 
similar  use. 

In  August,  1904,  two  reinforced  concrete  poles  were  made  for 
the  Schenectady  Railway  Company,  Schenectady,  N.  Y. 


14" 

X  iiyp' 


Length . =  35  ft. 

Cross-section  at  base . =  14"  x 

Cross-section  at  ground . =  1134^^ 

Cross-section  at  top . =  6"  x  6" 

1.33%  of  section. 

(Pole  No.  1.) 
1.68%  of  section. 
(  (Pole  No.  2.) 

Concrete,  a  wet  mixture  of  1  :  13^  ^  33^  Portland  cement,  sand,  and 
crushed  limestone. 

Age  at  test . =6  weeks. 


Longitudinal  steel  in  tension. 


i 


The  reinforcement  of  pole  No.  1  was  composed  of  twelve  ^g-inch 
square  twisted  steel  bars,  eight  of  which  were  arranged  in  a  circle 
and  enclosed  in  a  spiral  of  34"i^ch  twisted  steel,  with  a  pitch  of  3  to 
6  inches.  Four  of  the  bars  were  28  feet  long,  four  20  feet  long,  and 
the  four  remaining  bars,  placed  in  the  corners  outside  the  circle,  were 
full  length. 

Pole  No.  2  was  like  Pole  No.  1,  except  that  the  full-length  bars 
were  Y2  ii^ch  instead  of  ^  inch. 

An  accessible  point  on  the  railway  company’s  line  was  used  as  a 
casting  yard.  After  seasoning,  the  poles  were  handled  and  loaded 
by  a  crane  car,  carried  to  their  location  and  placed  by  the  crane  and 
an  auxiliary  gin  pole,  and  are  used  to  support  a  double-track  span 
construction  over  a  street.  Wooden  cross-arms,  placed  in  gains,  and 
supported  by  the  usual  metal  brackets,  are  used.  In  handling,  these 
poles  were  heavy  and  cumbersome,  several  cracks  appearing,  due  to 
the  large  taper  and  the  excessive  deflection.  The  reinforcement  was 
not  adequate  to  withstand  the  strains  due  to  lifting  into  position. 
These  poles  have  been  in  place  five  years  and  appear  to  be  in  as  good 
condition  as  when  first  installed,  no  signs  of  disintegration  appearing 
about  the  cracks  just  mentioned. 

In  November,  1905,  Wallace  Marshall,  of  Lafayette,  Ind.,  made 

18 


UNIVERSAL  PORTLAND  CEMENT  CO 


and  tested  one  pole.  This  test  pole  was  about  35  feet  long  and 
tapered  from  10  inches  square  at  the  ground  to  5  inches  square  at  the 
top,  with  chamfered  corners;  the  lower  5  feet,  10  inches  square,  was 
embedded  in  the  ground.  Bolts  were  placed  at  the  usual  heights  in 
the  forms  for  the  attachment  of  cross-arms,  line  bracket,  and  tele¬ 
phone  box.  On  top  and  in  the  center  was  placed  a  13^-inch  plug 
for  an  insulator  pin.  The  mixture  used  was  1  part  cement  to  6  parts 
of  graded  aggregate,  with  a  facing  of  13^  inches  of  1  :  3  mortar.  The 
reinforcement  consisted  of  four  ^-inch  Thacher  bars,  25  feet  long, 
and  four  3^-inch  Thacher  bars  14  feet  long,  with  a  lap  of  about  4 
feet.  The  forms  were  removed  at  the  expiration  of  six  days,  and  in 
thirty  days  the  pole  was  planted. 

For  purposes  of  comparison  a  large  cedar  telephone  pole  and  the 
concrete  pole  were  erected  25  feet  apart.  A  taut  wire  cable  con¬ 
nected  the  two  poles  at  a  height  of  21  feet  from  the  ground;  from  the 
middle  of  this  cable  was  suspended  a  barrel  which  received  the  test 
loads  in  the  shape  of  steel  rivets.  As  the  barrel  was  gradually  loaded 
with  rivets  the  two  poles  began  to  bend  toward  each  other.  When  the 
deflection  of  the  poles  was  about  21  inches,  a  small  check  or  crack 
appeared  in  the  concrete  pole  about  10  feet  from  the  ground,  followed 
by  others  from  the  ground  to  the  point  of  the  cable  attachment. 
At  this  point  in  the  test  the  load  was  removed  and  its  weight  ascer¬ 
tained. 

From  calculations  the  horizontal  load  was  found  to  be  about 
975  pounds  and  the  stress  in  the  reinforcement  about  equal  to  the 
elastic  limit  of  the  steel.  When  the  load  was  entirely  removed,  the 
pole  returned  to  its  original  position. 

In  1906,  R.  E.  Cummings,  of  Pittsburg,  Pa.,  made  for  G.  A, 
Cellar,  Superintendent  of  Telegraph  of  the  Pennsylvania  Lines  West 
of  Pittsburg,  a  comparative  test  of  two  cedar  and  two  concrete  poles. 
The  two  concrete  poles  were  hollow  for  two-thirds  of  their  length, 
but  had  a  solid  top.  The  shells  tapered  from  a  thickness  of  3  inches 
at  the  base  to  1^4  inches  at  the  solid  portion.  The  poles  had  cham¬ 
fered  corners  and  weighed  about  3500  pounds  apiece,  and  were 
designed*  to  withstand  any  stress  in  any  direction  that  would  be 
produced  by  a  line  of  50  wires,  each  wire  coated  with  ice  to  a  total 
diameter  of  1  inch;  i.  e.,  a  load  equivalent  to  1000  pounds  applied 
one  foot  below  the  top  of  the  pole.  The  two  cedar  poles  were  selected 
stock,  and  all  the  poles  were  set  in  a  concrete  foundation  3  feet 

*  On  a  50-wire  line,  under  a  loading  of  ^  inch  thickness  of  ice  and  a  wind 
pressure  of  8  pounds  per  square  foot,  the  equivalent  load  would  be  3100  pounds. 

19 


REINFORCED  CONCRETE  POLES 


square  and  5  feet  deep.  The  general  dimensions  of  the  four  poles 
and  a  record  of  the  tests  are  given  in  Table  4. 

TABLE  4.— LOADS  AND  CORRESPONDING  DEFLECTION  FOR  FOUR 

POLES  TESTED. 


Test 

No. 

Deflec¬ 

tion 

AT  Top, 
Inches. 

Load  in 
Pounds. 

Deflection 
AT  Bottom 

IN  Inches 
(12  inches 
above  ground¬ 
line). 

Time. 

Remarks. 

1 

30-foot  Octagonal  Concrete  Pole,  top  8  inches,  base  14  inches. 

(Depth  of  concrete  anchorage,  5  feet.  Load  applied  24'2"  from  ground.) 


/ 

3M 

1830 

1 

3  2 

3:17 

\ 

5M 

2230 

1 

1  6 

3:18 

f 

K 

50 

1 

35- 

8 

2630 

1 

J 

3:19 

1 

iiM 

3030 

3 

T6 

3:20 

f 

da 

50 

1 

T6 

1 

UA 

3430 

1 

? 

3:24 

18 

3210 

3 

J 

3:25 

1 

25  H 

3150 

3 

J 

3:26 

Temporary  deflection,  ]4,  inch. 

Cracks  Nos.  1  and  2. 

Temporary  deflection,  2  inches. 
Cracks,  Nos.  3  and  4. 

Crack,  No.  5,  crushed  at  bottom. 
Pole  broke  at  ground-line. 


30-foot  Square  Concrete  Poles,  top  7  inches,  base  13  inches. 

(Anchorage  and  point  of  application  of  load  same  as  before.) 


f 

50 

2:02 

1.  . 

i 

23^ 

1830 

2:04 

2230 

2:08 

f 

50 

2  .  . 

i 

4  A 

2630 

2:10 

8K 

3030 

1 

2:11 

f 

3K 

50 

3  .  . 

1 

31 

3290 

343^ 

3430 

1 

8 

2:14 

f 

21 M 

50 

4  .  . 

1 

39 

3690 

2:19 

Temporary  deflection,  1  inch. 


Crack,  No.  1. 

Tem.porary  deflection,  22  inches. 

Cracks,  2,  3,  4.  Pole  crushed. 
Cracked  at  ground-line. 


30-foot  Wooden  Pole,  No.  4,  White  Cedar,  top  8  inches,  base  14  inches. 

(Anchorage  and  point  of  application  of  load  same  as  before.) 


1 


20 

1830 

11:50 

22M 

2230 

11:51 

29 

2630 

11:52 

35 

2870 

11:53 

363^ 

2950 

11:54 

38^ 

3030 

11:55 

50 

3370 

11:56 

56 

3430 

11:57 

,  66 

3494 

12:00 

First  crack. 


Pole  broke  suddenly. 


W ooden  Pole,  No.  3,  White  Cedar,  top  8  inches,  base  14  inches. 


f 

14 

172 

1  .. 

37 

2230 

1 

47 

2530 

11:03 

Pole  broke  suddenly. 

20 


UNIVERSAL  PORTLAND  CEMENT  CO. 


The  reinforcement  consisted  of  four  %-inch  round  bars,  24  feet 
long,  and  four  ^-inch  round  bars  of  the  same  length.  The  taper  of 


Fig.  14. — Reinforced  concrete  poles  at  Maples,  Ind.,  P.  F.  W.  &  C.  Ry. 

the  concrete  poles  was  1  inch  in  5  feet.  Wooden  blocks  into  which 
the  galvanized  iron  steps  screwed  were  molded  into  the  concrete  at 

21 


REINFORCED  CONCRETE  POLES 


proper  intervals.  The  cross-arm  braces  were  fastened  to  the  pole 
in  the  same  manner,  by  a  lag-bolt,  and  attached  to  the  arms  by 
through-bolts.  The  load,  or  pull,  was  applied  by  means  of  a  wire 


OKTAILS  OF  REINFORCED  CONCRETE 
GRAPH  POLES. 

Fig.  15. — Poles  used  at  Maples,  Ind.,  P.  F.  W.  &  C.  Ry. 

rope  attached  to  an  iron  devise  placed  around  the  pole  10  inches  from 
the  top  and  drawn  over  a  pulley  placed  at  the  same  height. 

22 


UNIVERSAL  PORTLAND  CEMENT  CO 


*  “Experiments  with  Concrete  Telegraph  Poles,”  G.  A.  Cellar,  Proc.  Rwy. 
Tel.  Supts.,  1907. 


A  1  :  3  mixture  was  used,  the  poles  were  cast  in  cold  weather,  and 
suitable  gravel  was  not  obtained.  A 
defect  in  pole  No.  1  probably  caused 
its  early  rupture.  A  more  satisfactory 
result  was  obtained  from  the  test  of 
pole  No.  2. 

Mr.  Cellar  says:*  After  the  ce¬ 
ment  poles  had  been  broken,  the  re¬ 
inforcement  so  held  them  that  it 
required  almost  the  breaking  pressure 
to  further  deflect  them  from  their 
slightly  inclined  position.  The  wooden 
poles  under  strain  presented  the  form 
of  an  arch  before  breaking,  and  when 
they  gave  way  were  fractured  com¬ 
pletely;  but  these  features  were  lack¬ 
ing  in  the  cement  poles,  which  were 
very  firm  and  did  not  give  until  they 
began  to  crush  at  the  ground-line.’’ 

In  the  early  part  of  190G,  J.  B. 

McKim,  Superintendent  of  the  West¬ 
ern  Division  of  the  Pennsylvania  Lines 
West  of  Pittsburg,  built  a  line  of  53 
reinforced  concrete  telegraph  poles 
near  Maples,  Indiana,  along  the  Pitts¬ 
burg,  Fort  Wayne  and  Chicago  Rail¬ 
way.  These  poles  vary  in  height  from 
20  to  28  feet,  the  length  of  pole  above 
ground  varying  with  the  profile,  so 
that  the  telegraph  line  is  parallel  to 
and  at  a  constant  distance  above  the 
track.  The  poles  are  quite  small  in 
cross-section  and  are  of  minimum 
weight.  They  have  now  been  in  use 
four  years  and  show  no  signs  of  dete¬ 
rioration.  (Figs.  14  and  15.) 

At  the  present  time  several  hun¬ 
dred  concrete  poles  are  used  by  the  various  transmission  companies, 
in  distributing  to  interior  points  the  current  generated  by  Canadian 


23 


REINFORCED  CONCRETE  POLES 


1 


UNIVERSAL  PORTLAND  CEMENT  CO 


water-powers.  Examples  of  the  poles  erected  about 
Niagara  Falls  and  the  Welland  Canal  are  shown  in 
Figs.  16,  17,  18,  and  19. 

In  1903  the  Concrete  Pole  Company,  of  St. 
Catherines,  Ontario,  built  about  twenty  poles  for 
the  Niagara  Falls  Power  Company,  on  their  main 
line  to  Buffalo.  A  little  later  a  number  of  trans¬ 
mission  poles  were  built  for  the  Canadian  Niagara 
Power  Company,  at  Chippewa,  and  for  the  Ontario 
Power  Company,  at  Port  Robinson  and  Welland. 

In  1906  the  same  company  constructed  a  power 
line,  for  a  distance  of  12  miles,  for  the  Hamilton 
Power,  Light  and  Traction  Company.  The  poles 
are  35,  40,  45,  and  60  feet  in  total  length,  the  longer 
poles  being  used  at  road  and  other  crossings.  They 
are  spaced  about  200  feet  apart  and  carry  00  B.  &  S. 
gauge  copper  wires,  forming  two  3-phase  circuits  of 
40,000  volts.  These  poles  sustained  safely  a  test 
pull  of  2000  pounds  applied  at  the  top  of  the  pole. 
As  a  part  of  this  work  two  towers  150  feet  in  height 
— believed  to  be  the  highest  concrete  monoliths  in 
existence — were  successfully  constructed  on  each 
side  of  the  old  Welland  Canal,  to  carry  a  trans¬ 
mission  line  to  St.  Catherines,  Ontario.  These 
towers  are  guyed,  but  without  guys  can  safely 
withstand  a  pull  at  the  top  of  2000  pounds.  They 
are  embedded  8  feet  in  a  heavy  concrete  base, 
measure  11  inches  square  at  the  top  and  31  inches 
square  at  the  bottom,  and  carry  sixteen  No.  1  bare 
copper  wires  on  glass  insulators.  The  cross-arms 
are  of  concrete,  334  inches  by  4  inches  by  10  feet 
long.  A  platform  10  feet  long  by  5  feet  wide,  at 
a  convenient  distance  beneath,  enables  workmen 
to  make  inspection  and  adjustments  with  safety. 
The  canal  span  is  only  76  feet,  but  the  approach 
span  is  about  300  feet.  One  of  the  towers,  in  addi¬ 
tion  to  carrying  a  heavy  weight  of  wires  arranged 


Fig.  19. — 150  ft.  pole — 31  in.  base,  11  in.  top;  weight 
45  tons.  Welland  Canal  crossing  poles,  H.  P.,  L.  &  T.  Co. 

25 


REINFORCED  CONCRETE  POLES 


vertically  on  two  frames,  is  at  a  right-angled  bend  and  sustains  a 
heavy  angular  pull. 

In  1906  A.  C.  Chenoweth,  of  Brooklyn,  N.  Y.,  constructed 


Fig.  20. — Welland  Canal  crossing,  H.  P.,  L,  &  T.  Co. 

26 


UNIVERSAL  PORTLAND  CEMENT  CO. 


some  concrete  poles  60  feet  long  with  a  base  14  inches  in  diameter, 
designed  to  carry  a  direct  pull  of  16,000  pounds  and  the  torsional 
effect  of  an  arm  4  feet  long  carrying  8000  pounds.  These  poles 
carried  a  500-foot  span  of  4-inch  direct-current  transmission  cable, 
and  cost  about  $2.50  per  lineal  foot. 

The  Chenoweth  concrete  pole  is  rolled  by  a  specially  designed 
machine,  and  may  be  made  hollow  and  with  a  taper.  It  is  formed 
by  rolling  steel  wire  mesh  and  longitudinal  rods,  covered  with  con¬ 
crete,  into  a  coil. 

Reinforced  concrete  towers  of  rather  huge  proportions  were  erected 
in  1906  for  the  West  Penn  Railway  Company  for  their  transmission 
line  crossing  over  the  Monongahela  River  at  Brownsville,  Pa. 
One  structure  is  150  feet  in  height,  supporting  a  cable  span  of  1014 
feet,  at  an  average  height  of  105  feet  from  the  base  of  the  tower.  The 
tower  itself  is  guyed  to  an  anchor  tower  in  the  rear.  The  larger  main 
tower  has  a  foundation  30  feet  square  and  is  8  feet  6  inches  square  at 
the  top  of  the  foundation.  These  immense  poles  are  square,  hollow 
in  cross-section,  and  tapering.  Small  I  beams  constitute  the  rein¬ 
forcement  of  the  tower,  while  the  base  is  composed  of  a  large  slab,  re¬ 
inforced  by  a  meshwork  of  rods. 

In  1907  a  number  of  the  Seigwart  poles  were  tested  at  the  Olten 
Aarburg  electric  works.  One  of  the  poles  tested  carried  eight  No.  8 
wires,  the  pole  being  located  at  a  bend  in  the  line.  Of  a  total  length 
of  38  feet,  4  feet  8  inches  were  embedded  in  the  foundations.  In 
the  test  the  pole  was  placed  horizontally  between  two  large  concrete 
blocks,  a  pulley  block  being  attached  30  feet  from  the  point  of  grip, 
corresponding  to  the  top  of  the  foundation  or  surface  of  the  ground. 
A  dynamometer  was  used  to  measure  the  load.  In  Table  5  are  given 
the  results  of  the  first  test,  but  it  should  be  noted  that  during  this 
test,  that  portion  of  the  pole  held  within  the  foundation  blocks  twisted, 
and  when  the  strain  was  removed  the  pole  returned  to  within  an  inch 
of  its  original  position,  so  that  the  total  deflection  was  in  reality  more 
nearly  2.52  inches. 

TABLE  5. 


Pull  in  Deformation  Permanent 

PouNDg.  IN  Inches.  Deformation. 

88 . 0.00 

220 . 0.12 

440 . 0.32 

660 . 0.60 

880 . 1.12  _ 

1100 . 1.68 

1320 . 2.08  _ 

1540 . 3.52  _ 


27 


REINFORCED  CONCRETE  POLES 


A  second  test  was  made  on  the  pole  by  applying  the  load  in  two 
increments,  the  first,  of  88  pounds,  resulting  as  before  in  zero  de¬ 
flection,  and  the  second  load,  of  1540  pounds,  giving  a  deflection  of 
2.8  inches.  When  the  load  was  removed,  the  pole  returned  to  its 
first  position. 

As  a  final  test  the  pole  was  loaded  as  shown  in  Table  6. 

TABLE  6. 


Pull  in  Deformation  Permanent 

Pounds.  in  Inches.  Deformation. 

1540 . 2.84 

1760 . 3.6 

1980 . 5.4 

2200 . 6.2 


Under  the  extreme  condition  of  loading  it  was  found  that  the 
foundation  had  yielded,  so  that  the  actual  final  deflection  amounted 
to  about  4.8  inches. 

In  March,  1907,  the  United  Traction  Company,  of  Albany,  made 
further  tests  of  several  reinforced  concrete  poles.*  These  poles  were 
all  alike  in  cross-section  and  length,  the  arrangement  of  cross-arms 
and  kind  of  reinforcement  distinguishing  the  different  poles. 

Pole  No.  1,  illustrated  in  Figs.  21,  22,  and  23,  is  a  type  of  concrete 
pole  between  trolley  tracks  which,  in  addition  to  carrying  on  the 
lower  arm  a  catenary  suspension  trolley  line,  supports  two  feeder 
wires  and  a  3-phase  transmission  line.  Standard  insulator  pins  were 
used,  the  one  at  the  top  cast  in  place,  and  the  others  placed  in  cored 
holes  in  the  arms.  This  construction  is  entirely  of  reinforced  con¬ 
crete.  The  reinforcement  of  the  pole  proper  was  of  the  rectangular 
cage  construction.  Four  ^-inch  square  bars,  running  the  full 
length  of  the  pole,  were  fabricated  into  a  square,  by  right  and  left 
turns  of  a  double  coil  of  No.  12  wire,  having  a  pitch  of  about  3  inches, 
and  tied  frequently  to  the  main  rods.  The  lower  arm  was  reinforced 
with  four  3^-inch  square  twisted  bars  and  No.  14  wire,  having  a  right 
and  left  pitch  of  2  inches.  In  the  upper  arms  and  brackets  four 
S/g-inch  bars  and  No.  14  wire  were  used.  The  steel  of  the  cross- 
arms  and  brackets  was  tied  to  the  main  pole  reinforcement,  thus 
constituting  a  unit  skeleton  frame.  The  minimum  distance  between 
the  main  bars  and  the  surface  of  the  concrete  was  1  inch. 

After  the  pole  had  attained  an  age  of  fifty-five  days,  a  horizontal 
load  or  pull  was  applied  about  20  feet  6  inches  from  the  ground,  or 
6  inches  above  the  lower  arm. 

*  Abstracted  from  data  prepared  by  C.  T.  Middlebrook,  M.  Am.  Soc.  C.  E. 

28 


UNIVERSAL  PORTLAND  CEMENT  CO. 


Fis:.  21. — Outline  plan  of  reinforced  concrete  pole,  designed  for  electric  rail¬ 
way  service,  double  track  carrying  high-tension  transmission  line.  Pole  designed 
to  take  pull  of  500  lbs.  at  21  feet  from  ground  with  factor  of  safety  of  four,  or 
1000  lbs.  at  two-thirds  the  elastic  limit  of  the  steel;  steel,  400  lbs. ,  concrete,  20 
cu.  ft.  Concrete  proportions;  1  part  Portland  cement,  l  A  ^oono 

3  parts  crushed  stone,  not  over  one-half  inch  m  size.  Weight  of  pole,  3200  lbs. 


29 


REINFORCED  CONCRETE  ROLES 


Fig.  22. — Test  of  United  Traction  Co.  pole. 


30 


UNIVERSAL  PORTLAND  CEMENT  CO. 


At  a  convenient  point  a  dynamometer  was  placed  to  measure 
the  various  loads  corresponding  to  the  deflections  in  the  pole.  A 
plumb-bob  was  suspended  from  a  point  on  the  pole  at  the  same  dis¬ 
tance  above  the  ground  as  the  point  of  application  of  the  load. 

TABLE  7. 


Load 

(Pounds). 

Deflection 

(Inches). 

Bending 

Moment 

(Inch- 

Pounds).* 

Unit 

Tension, 

Steel.* 

Unit 

Compression, 

Steel.* 

Unit 

Comp., 

Con¬ 

crete.* 

Arm. 

200 . 

H 

49,200 

7,048 

2,420 

320 

20.5  ft. 

425 . 

104,550 

15,000 

5,100 

640 

600 . 

5f 

147,600 

21,100 

7,200 

900 

800 . 

8 

196,800 

28,200 

9,600 

1,200 

1000 . 

10^ 

246,000 

35,200 

12,100 

1,500 

.... 

The  compression  of  the  soil  at  the  foot  of  the  pole  increased  the 
total  observed  deflection.  An  opening  3^  inch  wide  appeared  in  the 
ground  at  the  base  of  the  pole  on  the  tension  side.  When  all  the 
load  was  removed,  the  pole  returned  to  within  134  inches  of  its  first 
position,  this  amount  undoubtedly  being  the  measure  of  the  compres¬ 
sion  of  the  soil.  When  the  load  reached  1000  pounds,  a  few  minute 
cracks  appeared  following  the  hair  cracks.  These  cracks  were  cut 
into  with  a  cold  chisel,  before  the  load  was  removed,  and  water  was 
applied  in  an  attempt  to  ascertain  to  what  extent  it  v/ould  be  ab¬ 
sorbed  by  the  cracks.  The  cracks  did  not  appear  to  be  more  than 
34  inch  deep. 

After  three  weeks  had  elapsed  this  pole  was  again  subjected  to  a 
second  test,  the  load  being  gradually  increased  to  1000  pounds,  with 
about  the  same  deflections  as  in  the  first  test.  Another  increment 
was  added,  making  the  load  1375  pounds,  and  producing  a  deflection 
of  13  inches.  No  cracks  were  observed  except  those  noted  in  the 
first  test.  While  under  a  load  of  1375  pounds  the  cracks  were 
again  examined  with  a  cold  chisel  for  a  depth  of  inch.  Beyond 
this  depth  there  were  no  evidences  of  cracks.  Mr.  C.  T.  Middle- 
brook,  who  conducted  the  tests,  remarks  that  ^^as  the  stretch  of 
the  steel  on  the  tension  side  under  this  pull  amounted  to  about 
0.00167  of  its  length,  or  about  -gV  of  an  inch  per  foot,  it  would 
appear  that  the  particles  of  aggregate  must  adjust  themselves, 
under  tensile  stress,  in  such  a  manner  as  to  render  the  detection 
of  cracks  in  the  body  of  the  concrete,  even  when  comparatively 
near  the  surface,  much  more  different  than  in  the  rich  mortar 

*  Computed  for  comparison  by  the  authors. 

31 


REINFORCED  CONCRETE  POLES 


surface  itself.”  On  the  removal  of  the  load,  the  pole  returned  to 
its  original  position,  except  for  the  permanent  deflection  due  to  the 


Fig.  23. — United  Traction  Co.  pole. 


compression  of  the  soil.  These  tests  were  considered  successful 
for  a  pole  under  horizontal  loading. 

32 


UNIVERSAL  PORTLAND  CEMENT  CO 


The  cross-arms  were  tested  by  loading  each  arm  at  a  point  7  feet 
6  inches  from  the  center  of  the  pole,  with  increasing  weights  up  to 
800  pounds,  without  any  serious  torsional  effects.  It  was  concluded 
that  the  spiral  webbing  was  ample  provision  against  strains  of  this 
nature. 

Pole  No.  2  was  like  pole  No.  1,  except  for  the  arrangement  and 
quantity  of  steel.  Four  %-inch  round  Bessemer  rods  were  used  with 
right  and  left  binding  coils;  but  in  order  to  test  the  effectiveness  of 
the  tie  between  the  main  bars  and  the  coils,  full-length  ^-inch  [’s 
were  clamped  to  the  corner  bars  by  shrinking  on  3^-inch  by  }/8-inch 
steel  straps  at  1-foot  intervals.  The  combined  area  of  two  bars  and 
two  channels  was  1.52  square  inches,  effective  in  tension,  as  compared 
with  1.12  square  inches  of  pole  No.  1. 

It  is  quite  probable  that  the  total  area  of  1.52  inches  was  not 
entirely  effective  on  account  of  the  difficulty  in  getting  the  concrete 
mixture  between  the  y^-moh.  bar  and  its  enclosing  channel,  and  thus 
assuring  a  proper  bond. 

Compared  with  pole  No.  1  the  deflections  were  much  greater 
for  the  same  loads,  and  at  1000  pounds  there  were  signs  of  incipient 
failure,  a  crack  opening  on  the  tension  side  1  foot  from  the  ground¬ 
line.  When  1300  pounds  was  reached,  the  largest  reading  for  this 
pole,  the  crack  widened,  apparently  indicating  the  yield  point  of  the 
steel.  On  removing  the  load  the  pole  did  not  recover  more  than  a 
few  inch.es  of  its  deflection,  remaining  30  inches  out  of  plumb. 


TABLE  8.— POLE  No.  2. 


Arm. 

(feet;. 

Pull 

(Pounds). 

Bending 

Moment. 

Deflection 

(Inches). 

Unit 

Tension, 

Steel. 

Unit 

Comp., 

Steel. 

Unit 

Comp., 

Concrete 

20.5 

1,000 

246,000 

13 

27,000 

8,900 

1,240 

20.5 

1,300 

319,800 

15 

35,000 

11,500 

1,610 

There  were  no  evidences  of  failure  of  the  concrete  on  the  com¬ 
pression  side  opposite  the  point  of  failure  of  the  steel,  although  at 
the  latter  point  the  concrete  was  badly  disintegrated,  the  crack  ex¬ 
tending  half-way  through  the  pole.  The  spiral  winding  hoops 
probably  increased  the  compressive  resistance  of  the  concrete. 

The  poles  were  made  in  substantial  2-inch  spruce  forms,  well 
dressed  and  oiled  and  supported  horizontally.  They  were  cast  and 
cured  in  a  dry,  steam-heated  atmosphere,  the  mixture  being  1  : 4 
Portland  cement  and  limestone  screenings,  J^-inch  maximum,  with  a 
,  33 


REINFORCED  CONCRETE  POLES 


UNIVERSAL  PORTLAND  CEMENT  CO. 


small  amount  of  sand.  All  the  poles  showed  hair  cracks,  probably 
due  to  the  atmosphere  in  which  they  were  cured  and  to  the  presence 
of  loam  or  other  impurities  in  the  crusher  dust.  In  setting,  the  poles 


Fig,  25. — Oklahoma  Gas  and  Electric  Co.  line. 


were  embedded  6  feet  in  the  ground,  and  some  concrete  was  placed 
around  the  pole  to  increase  its  resistance. 

From  a  comparison  of  the  tests  of  poles  No.  1  and  No  2,  it  would 
appear  that  the  cold  twisted  square  bars  in  pole  No.  1  had  about  twice 
the  elastic  limit  of  the  commercial  Bessemer  rounds  in  pole  No.  2, 

35 


REINFORCED  CONCRETE  POLES 


Fig.  26. — Oklahoma  Gas  and  Electric  Co.  poles. 


36 


UNIVERSAL  PORTLAND  CEMENT  CO. 


and  gave  better  results,  though  the  percentage  of  reinforcement  was 
0.23  per  cent.  less. 


TABLE  9.— POLE  No.  1. 


Normal 

Arm 

Unit  Tension 

Unit  Comp. 

Unit  Concrete  Comp. 

X  U  L  L 

(Pounds). 

(i'EET). 

(Pounds). 

(Pounds). 

(Pounds). 

550 

20.5 

20,000 

8,000 

1,000 

1375 

20.5 

50,400 

19,800 

2,600 

The  elastic  limit  of  the  cold  twisted  steel  bars  was  about  55,000 
pounds  per  square  inch.  Inasmuch  as  the  surface  cracks  developed 


Fig.  27. — Oklahoma  Gas  and  Electric  Co.  forms. 


at  1375  pounds  were  not  large  or  deep  enough  to  admit  moisture,  it 
would  seem  economical  to  use  a  bar  having  a  mechanical  bond  and 
steel  of  a  high  elastic  limit.  Pole  No.  1  was  designed  for  a  normal 
pull  of  550  pounds. 

In  the  summer  and  fall  of  1908  G.  A.  Cellar,  superintendent  of 
telegraph  of  the  Pennsylvania  Lines  West  of  Pittsburg,  had  designed 
and  erected  a  reinforced  concrete  pole  line  through  the  town  of  New 
Brighton,  Pa.  The  poles  are  square  in  section  with  chamfered  cor- 
They  are  35  feet  long,  with  a  width  at  the  top  of  6  inches  and 

37 


ners. 


REINFORCED  CONCRETE  POLES 


a  width  at  the  base  of  14  inches;  the  slope  increasing  toward  the  butt 
1  inch  for  each  5  or  6  feet  of  length,  depending  upon  the  conditions  of 
loading  used  and  the  allowable  stresses. 

The  Oklahoma  Gas  and  Electric  Company  have  installed  as  a 
part  of  their  permanent  construction  a  number  of  reinforced  concrete 
poles,  shown  in  Figs.  25,  26,  27. 


Fig.  28. — Filling  form  with  concrete.  Fig.  29. — Form  after  being 

filled  with  concrete. 

The  poles  are  hollow,  hexagonal  in  section,  measuring  for  a  35- 
foot  pole  7  inches  maximum  diameter  at  the  top  and  1-6  inches  at  the 
bottom.  The  reinforcement  consists  of  twelve  J^-inch  high-carbon 
steel  rods,  with  mechanical  bond,  arranged  symmetrically  about  the 
center.  At  each  end  of  the  pole  the  rods  are  held  in  position  by  pass¬ 
ing  the  ends  through  top  and  bottom  plates  and  bending  down  the 

38 


UNIVERSAL  PORTLAND  CEMENT  CO. 


ends.  Another  plate  is  placed  on  the  turned-down  ends  and  bolted 
to  the  spacing  plate.  Before  the  butt  plate  attachment  is  made  the 
rods  are  stretched  and  anchored  by  10-inch  pieces  of  rod  with  an  eye 
made  at  one  end  and  threaded  at  the  other,  the  reinforcing  rods 
being  hooked  into  the  eyes.  Short  pieces  of  pipe  over  the  stretchers 


Fig.  30. — Face  of  form  removed  after  Fig.  31. — Thirty-foot  concrete  pole, 
four  days. 


butt  against  the  steel  plate.  Nuts  and  washers  are  screwed  down  on 
the  outer  end  of  the  pipe,  producing  an  initial  tension  in  the  rods. 
The  core  is  suspended  by  wires  in  the  center  of  the  outer  forms  and 
is  covered  with  one  thickness  of  building  paper;  concrete  of  a  1  :  2  :  3 
mixture  is  then  added.  Three  parts  of  chats  or  zinc  tailings  are 

39 


REINFORCED  CONCRETE  POEES 


mixed  with  the  cement  and  sand  and  are  obtained  at  reasonable  cost 
and  quantity  from  the  local  zinc  mines  of  southwestern  Missouri. 
This  company  claims  to  make  the  35-foot  poles  at  a  cost  of  $10  with 
cement  at  $1.50  per  barrel,  sand  at  $2.00  per  cubic  yard,  chats  at 
$2.00  per  cubic  yard,  and  labor  at  $2.00  per  day. 

The  American  Concrete  Pole  Company  of  Richmond,  Indiana, 
have  constructed  for  the  local  traction  company,  the  Terre  Haute, 
Indianapolis  and  Eastern  Traction  Company,  some  forty-three  re¬ 
inforced  concrete  poles,  varying  from  14  to  60  feet  in  height.  Figs. 
28,  29,  30,  and  31  show  the  various  stages  of  construction.  For  poles 
under  35  feet  in  height  this  company  claims  that  it  is  economical  to 
mold  the  poles  on  the  ground  and  erect  by  derrick.  Poles  exceeding 
35  feet  in  height  are  cast  in  their  final  vertical  positions,  so  that 
when  the  forms  are  removed  the  pole  is  ready  for  service.  The 
forms  are  constructed  of  wood  and  iron  so  put  together  as  to  pre¬ 
vent  warping  and  give  a  smooth  exterior  surface.  One  side  of  the 
form  is  removable  to  aid  in  placing  firmly  and  accurately  the  four 
longitudinal  reinforcing  rods.  A  continuous  spiral  of  binding  wire 
extending  from  top  to  bottom  forms  the  web  reinforcement. 

In  this  locality  it  is  claimed  that  a  45-foot  pole  ready  for  use  costs 
$25,  while  in  the  same  locality  a  dressed  cedar  pole  in  position  costs 
$22.50.  Under  local  conditions  this  company  makes  the  following 
comparative  estimate  of  the  cost  of  work  actually  done  in  the  con¬ 
struction  of  trolley  poles. 


TABLE  10.— COMPARATIVE  ESTIMATED  COST  OF  REINFORCED 
CONCRETE  AND  CEDAR  POLES.  (Cost  of  Concrete  Poles  is 

WITHOUT  Royalty.) 


CONCRETE  POLES. 


Length. 

Top. 

Bottom. 

Steel. 

Cu.  Ft. 
Concrete. 

Cost 

Steel. 

Cost 

Concrete. 

Cost  Bail 
WTre. 

Labor. 

Total 

Cost. 

Feet. 

25 

Inches. 

6 

Inches. 

10 

Inches. 

16 

$1.57 

$2.24 

$1.20 

$4.70 

$9  71 

30 

6 

11 

21 

2.29 

2.94 

1.20 

5.20 

11.63 

35 

6 

12 

26 

3.91 

3.64 

1.20 

5.70 

14.45 

40 

7 

15 

M 

36 

6.31 

5.04 

1.50 

7.20 

20  05 

45 

7 

16 

K 

43 

8.56 

6.02 

1.50 

8.70 

24.78 

50 

7 

17 

% 

50 

9.50 

7.00 

1.80 

10.20 

29.50 

55 

7 

18 

1 

56 

13.34 

7.84 

1.80 

11.95 

34.95 

60 

7 

19 

1 

61 

14.56 

8.54 

1.80 

14.70 

40.60 

40 


UNIVERSAL  PORTLAND  CEMENT  CO. 


CEDAR  POLES. 


Length. 

Top. 

CQ 

d 

d 

Labor. 

Total 

Cost 

Feet 

25 

Inches. 

7 

$2.60 

(Dressed,  graved,  ruffed,  bored, 

$1.50 

$4.10 

30 

7 

6.25 

hauled,  and  set.) 

2.00 

8.25 

35 

7 

8.75 

2.40 

11.15 

40 

8 

12.00 

3.50 

15.00 

45 

8 

17.20 

5.00 

22.20 

50 

8 

20.20 

6.50 

26.70 

55 

8 

24.80 

8.50 

33.30 

60 

8 

29.75 

10.00 

39.75 

The  American  Concrete  Pole  Company,  of  Richmond,  Ind., 
made  a  comparative  test  of  one  of  their  30-foot  poles  and  a  cedar 
pole  of  the  same  size.  The  pole  was  of  square  cross-section,  7  inches 
at  the  top  and  12  inches  at  the  ground-line.  The  base  of  the  pole 
was  embedded  in  the  ground  for  a  distance  of  5  feet  and  thoroughly 
braced.  The  reinforcement  consisted  of  four  5^-inch  twisted  steel 
rods  of  high  elastic  limit,  bound  together  with  No.  9  binding  wire. 


TABLE  11.— CONCRETE  POLE. 


Pull  in  Deformation  Permanent 

Pounds.  in  Inches.  Deformation. 

840 .  6 

1780 . 17 

2800 . 30 

3640 . 36 

7200 . 60 


Pole  deflected  over  6  feet  before  failing. 
TABLE  12.— CEDAR  POLE. 


Pull  in  Pounds.  Deformation  in  Inches.  Permanent  Deformation., 

840 . -....ll 

1780 . 33 

2200 . 42 


Pole  broke  at  last  load  at  ground-line. 

In  the  final  stages  of  the  test,  the  concrete  crumbled,  allowing  the 
rods  to  bend. 


Design  of  Concrete  Poles. 

Before  entering  upon  any  detailed  discussion  of  design,  it  is 
necessary  to  consider  briefly  the  forces  acting  upon  a  pole  line  and 
the  character  of  service  required  of  its  component  parts.  As  al¬ 
ready  stated,  the  function  of  the  pole  is  that  of  a  cantilever  beam, 
rather  than  a  column.  The  external  forces  are  due  to  dead,  ice, 

41 


REINFORCED  CONCRETE  POLES 


and  wind  loads,  which  with  the  exception  of  the  pressure  on  the  pole, 
must  be  transmitted  to  the  pole  by  the  wires. 

The  weight  of  the  wires  and  their  coating  of  sleet,  together  with 
the  weight  of  cross-arms,  insulators,  and  the  pole  itself,  is  a  vertical 
load,  which  the  pole  carries  as  a  column.  The  pressure  of  the  wind, 
on  the  wires  whose  diameter  is  increased  by  the  sleet,  and  upon  the 
pole  structure,  is  assumed  as  acting  horizontally  and  at  a  right  angle 
with  the  line.  The  above  vertical  and  horizontal  forces  act  together 
upon  the  pole,  but  since  the  horizontal  forces  are  applied  at  the  wires, 
and,  therefore,  near  the  top  of  the  pole,  their  effect  is  much  greater 
than  the  effect  of  the  vertical  forces. 

In  the  case  of  a  pole  placed  at  a  bend  in  the  line,  there  must  be 
added  to  the  foregoing  the  horizontal  component  of  the  tension  in  the 
wires,  ^.  e.,  the  maximum  tension  multiplied  by  twice  the  sine  of 
one-half  the  angle  of  the  bend. 

Again,  in  case  the  sags  in  adjoining  spans  are  not  so  adjusted  as  to 
balance  the  tension  of  the  wires  either  side  of  the  pole,  there  will  be 
an  unbalanced  pull  in  the  direction  of  the  line,  which  must  be  con¬ 
sidered  in  conjunction  with  the  vertical  and  horizontal  forces  first 
mentioned.  Unbalanced  tension  may  also  be  produced  by  unequal 
ice  and  wind  loads  in  adjoining  spans. 

If  it  is  further  assumed  that  all,  or  part,  of  the  wires  may  be  broken 
by  excessive  loading,  faulty  material,  or  by  burning,  then  the  pole 
must  withstand  a  longitudinal  force  equal  to  the  tension  in  the  wires 
in  the  unbroken  span.  This  condition  is  fortunately  very  unusual, 
and  is  not  generally  taken  into  account  on  intermediate  poles. 

The  usual  attachments  for  fastening  line  wires  to  the  insulators 
do  not  have  sufficient  strength  to  develop  the  ultimate  stress  of  the 
wire,  and,  therefore,  a  broken  wire  would  pull  through  into  the  ad¬ 
joining  spans  before  exerting  its  maximum  tension  upon  the  poles. 
As  a  matter  of  economy,  it  is  usually  better  to  dead-end  the  wires 
and  poles  at  intervals  and  confine  the  effects  of  broken  wires  to  the 
section  in  which  the  break  occurs,  rather  than  make  every  pole  and 
attachment  of  sufficient  strength  to  dead-end  the  line. 

In  addition,  it  can  be  shown  by  a  rather  complicated  mathe¬ 
matical  demonstration  that,  owing  to  certain  properties  of  the  cate¬ 
nary  curve,  a  slight  bending  in  a  number  of  poles  will  balance  the 
tensions  in  adjoining  spans. 

‘^Omitting  from  consideration  the  effects  of  tornadoes  and  cy¬ 
clones,  it  is  necessary  to  determine,  or  assume,  the  maximum  velocity 
of  the  wind,  for  general  practice,  or  for  any  particular  locality.  .  .  . 

42 


UNIVERSAL  PORTLAND  CEMENT  CO. 


The  records  of  the  United  States  Weather  Bureau — omitting 
tornadoes,  cyclones,  and  violent  gales  occurring  in  some  particularly 
exposed  situations — give  a  maximum  indicated  velocity  of  100  miles 
per  hour.  .  .  .  Table  13  shows  the  maximum  velocities  observed 

at  a  number  of  stations  by  the  United  States  Weather  Bureau.’'* 


TABLE  13. 


Observatory. 

Period. 

Maximum 

Velocity 

Indicated. 

Observatory. 

Period. 

Maximum 

Velocity 

Indicated. 

Chicago,  Ill . 

1871-1906 

90 

Savannah,  Ga. . . 

1894-1903 

76 

Buffalo,  N.  Y.  . . . 

1871-1907 

90 

Philadelphia,  Pa. 

1872-1907 

75 

Galveston,  Tex.  .  . 

1894-1903 

84 

Bismarck,  N.  D. . 

1894-1903 

72 

New  York,  N.  Y. 

1871-1907 

80 

Boston,  Mass.  .  . 

1873-1907 

72 

Eastport,  Me.  .  .  . 

1873-1907 

78 

Salt  Lake  City, 
Utah . 

1894-1903 

60 

A  tabulation,  by  months,  of  the  highest  indicated  velocities 
recorded  by  the  United  States  Weather  Bureau,  at  the  New  York 
City  Station,  from  1884  to  1906,  and  of  the  number  of  different 
twelve-hour  periods,  during  which  a  maximum  velocity  of  60  miles, 
or  more,  was  observed,  from  1895  to  1906,  shows  that: 

The  maximum  velocity  of  80  miles  per  hour  occurred  during  a 
sleet-storm. 

The  maximum  velocities  occur  during  the  winter  months,  when 
sleet  may  be  on  the  wires. 

Indicated  velocities  of  more  than  80  miles  per  hour  will  rarely, 
if  ever,  occur  during  the  life  of  a  given  structure. 

Indicated  velocities  of  from  65  to  75  miles  per  hour  may  be 
expected  several  times  each  year,  though  much  less  frequently  in 
conjunction  with  sleet. 

In  Table  14  are  given  the  equivalent  actual”  velocities  cor¬ 
responding  to  those  ‘‘indicated”  by  anemometer  readings,  and  the 
pressures  per  square  foot  produced  on  flat  and  cylindrical  surfaces. 

Experience  in  sleet-storms  indicates  that  generally  throughout 
this  country  a  deposit  of  ice  of  about  j/^-inch  thickness  may  be  ex¬ 
pected  at  irregular  intervals.  Greater  thicknesses  are  sometimes  en¬ 
countered,  but  the  heavier  deposits  are  usually  snow-ice  of  lighter 
weight,  and  with  less  adhesion  to  the  wires.  It  may  reasonably 
be  expected  that  a  portion,  at  least,  of  these  larger  accretions  will  be 
broken  off  by  the  rising  wind,  so  that  the  final  average  load  on  a  span 

*  “Overhead  Construction  for  High-tension  Electric  Traction  or  Transmis¬ 
sion,”  by  R.  D.  Coombs,  Trans.  Am.  Soc.  C.  E.,  vol.  lx. 

43 


REINFORCED  CONCRETE  POLES 


will  be  approximately  equivalent  to  a  uniform  thickness  of  Y2  inch 
of  clear  ice. 

To  a  certain  extent  the  thickness  of  ice  is  independent  of  the 
diameter  of  the  wire,  though  it  has  sometimes  been  assumed  that  a 
thickness  equal  to  the  diameter  would  occur.  This  is  manifestly 
wrong  for  the  smaller  sizes  of  wire,  as  is  proved  by  the  coating  of 
twigs  in  every  sleet-storm,  and  by  actual  experience  with  line  wires. 


TABLE  14.— WIND  PRESSURES  AND  VELOCITIES. 


Indicated 
Velocity,  Miles 
Per  Hour. 

Actual 

Velocity,  Miles 
Per  Hour. 

Pressure  per  sq.  ft. 
ON  Cylinders. 

P  =  .0025V2. 

Pressure  per  sq.  ft. 
ON  Flat  Surfaces. 

P  =  .0042V2. 

30 

25.7 

1.7 

2.8 

40 

33.3 

2.8 

4.6 

50 

40.8 

4.2 

7.0 

60 

48.0 

5.8 

9.7 

70 

55.2 

7.6 

12.8 

80 

62.2 

9.7 

16.2 

90 

69.2 

12.0 

20.1 

100 

76.2* 

14.6 

23.3 

no 

83.2* 

17.3 

29.1 

120 

90.2* 

20.3 

34.2 

TABLE  15.— ICE  AND  WIND  LOADS  ON  WIRES. f 


COPPER  WIRE— SOLID. 


Gauge 

B.  &  S. 

Breaking 

Strength. 

Load  Per  Lin.  Ft. 
Vertical. 

Load  Per.  Lin.  Ft. 
Horizontal. 

Max.  Load  Per 
Lin.  Ft.  Plane 
OF  Resultant. 

Hard-drawn. 

1 

Soft-drawn. 

Dead. 

Dead  -f-  Y  Ice. 

Dead  -1-  f"  Ice. 

15.0  lbs. 

P.  Sq.  Ft. 

02  « 

OQ  C 

£  o 

q  J" 

00  Pm 

11.0  lbs.  P.  Sq. 
Ft.,  on  f'  Ice. 

Dead,  15  lbs. 
Wind. 

Dead,  Ice, 

8  lbs.  Wind. 

Dead,  f"  Ice, 

11  lbs.  Wind. 

0000 . 

8310 

5650 

0.641 

1.238 

1.770 

0.575 

0.973 

1.797 

0  861 

1.575 

2.522 

000 . 

6590 

44800.509 

1.074 

1.591 

0.512 

0.940 

1.750 

0.722 

1.427 

2.365 

00 . 

5220 

3555 

0.403 

0.940 

1.443 

0.456 

0.910 

1.709 

0.608 

1.309 

2.237 

0 . 

4560 

2820 

0.320 

0.833 

1.323 

0.406 

0.883 

1.673 

G.517 

1.214 

2.133 

1 . 

3740 

2235 

0.253 

0.744 

1.223 

0.362 

0.860 

1.640 

0.442 

1.137 

2.046 

2 . 

3120 

1770 

0.202 

0.673 

1.142 

0.322 

0.838 

1.611 

0.380 

1.075 

1.975 

3 . 

2480 

1405 

0.159 

0.613 

1.073 

0.287 

0.820 

1.585 

0.328 

1.024 

1.914 

4 . 

1960 

1115 

0.126 

0.564 

1.016 

0.255 

0.803 

1.562 

0.284 

0.981 

1.863 

5 . 

1560 

885 

0.100 

0.524 

0.969 

0.227 

0.788 

1.542 

0.248  0.946 

1.821 

6 . 

1240 

700 

0.079 

0.491 

0.930 

1 

0.203 

0.775 

1.524 

0.218  0.917 

1.785 

*  Added  by  comparison. 

t  Abstract  from  wire  tables,  Fitzpatrick  and  Coombs,  Engineers  and  Contrac* 
tors,  1123  Broadway,  New  York. 


44 


UNIVERSAL  PORTLAND  CEMENT  CO. 


TABLE  16.~ICE  AND  WIND  LOADS  ON  WIRES. 


COPPER  WIRE— STRANDED. 


Gauge 

B.  &  S. 

Breaking 

Strength. 

Load  Per.  Lin.  Ft. 
Vertical. 

Load  Per.  Lin.  Ft. 
Horizontal. 

Max.  Load  Per 
Lin.  Ft.  Plane 
OF  Resultant. 

Hard-drawn. 

Soft-drawn. 

Dead. 

Dead  -f  Y'  Ice. 

Dead  -1-  f"  Ice. 

15.0  lbs. 

P.  Sq.  Ft. 

8.0  lbs.  P.  Sq. 

Ft.,  on  Y  Ice. 

11.0  lbs.  P.  Sq. 

Ft.,  on  f"  Ice. 

Dead,  15  lbs. 

Wind. 

Dead,  1"  Ice, 

8  lbs.  Wind. 

Dead,  f"  Ice, 

11  lbs.  Wind. 

500,000 . 

23,540 

13,340 

1.525 

2.345 

2.989 

1.024 

1.213 

2.126 

1.837 

2.640 

3.668 

450,000 . 

21,210 

12,020 

1.373 

2.163 

2.791 

0.963 

1.180 

2.081 

1.677 

2.464 

3.481 

400,000 . 

18,860 

10,680 

1.220 

1.984 

2.599 

0.910 

1.152 

2.042 

1.522 

2.294 

3.305 

350,000 . 

16,500 

9350 

1.068 

1.801 

2.401 

0.849 

1.119 

1.997 

1.364 

2.120 

3.123 

300,000 . 

14,160 

8025 

0.915 

1.618 

2.203 

0.788 

1.087 

1.953 

1.208 

1.949 

2.944 

250,000 . 

11,790 

6680 

0.762 

1.440 

2.012 

0.738 

1.060 

1.916 

1.061 

1.788 

2.778 

0000 . 

9970 

5650 

0.645 

1.286 

1.831 

1.663 

1.020 

1.861 

0.925 

1.641 

2.611 

000 . 

7910 

4480 

0.513 

1.116 

1.651 

0.588 

0.980 

1.806 

0.780 

1.485 

2.446 

00 . 

6270 

3555 

0.406 

0.978 

1.498 

0.525 

0.947 

1.760 

0.664 

1.361 

2.311 

0 . 

4970 

2820 

0.322 

0.866 

1.372 

0.469 

0.917 

1.719 

0.569 

1.261 

2.199 

1 . 

3940 

2235 

0.255 

0.771 

1.263 

0.413 

0.887 

1.678 

0.485 

1.175 

2.100 

2 . 

3130 

1770 

0.203 

0.695 

1.174 

0.3640.861 

1.642 

0.417 

1.107 

2.019 

3 . 

2480 

1405 

0.160 

0.633 

1.103 

0.326  0.841 

1.614 

0.363 

1.053 

1.955 

4 . 

1970 

1115 

0.127 

0.582 

1.042 

0.289 

0.821 

1.587 

0.316 

1.006 

1.899 

5.. . 

1560 

885 

0.101 

0.540 

0.992 

0.258 

0.804 

1.564 

0.277 

0.970 

1.852 

6 . 

1235 

700 

0.080 

0.505 

0.951 

0.230 

0.789 

1.543 

0.243 

0.936 

1.813 

TABLE  17.— ICE  AND  WIND  LOADS  ON  WIRES. 

COPPER  WIRE— SOLID,  TRIPLE  BRAID  WEATHER-PROOFING. 


Breaking 

Strength. 

Load  Per.  Lin.  Ft. 
Vertic.al. 

Load  Per. Lin.  Ft. 
Horizontal. 

Max.  Load  Per. 
Lin.  Ft.  Plane 
OF  Result.ant. 

Gauge 

CJ 

O 

oJ 

^  (a3 

CQ 

B.  &  S. 

& 

• 

.  H-t 

£ 

c3 

u 

c3 

u 

P5|’^ 

CQ 

p-l  H|« 

ic’S 

1-H  d 

K 

1 

s-i 

O 

P 

Dead  + 

Dead  -I- 

o 

S'® 

8.0  lbs. 
Ft.,  on 

11.0  lbs 
Ft.,  on 

•  ^ 

0) 

Q 

Dead, 
8  lbs. 

Dead, 
11  lbs. 

0000 . 

8310 

5650 

0.767 

1.476 

2.064 

0.800 

1.093 

1.961 

1.108 

1.837 

2.847 

000 . .  . 

6590 

4480 

0.629 

1.309 

1.8820.741 

1.062 

1.918 

0.972 

1.686 

2.687 

00 . 

5220 

3555 

0.502 

1.133 

1.682  0.644 

1.010 

1.847 

0.818 

1.518 

2.498 

0 . 

4560 

2820 

0.407 

1.029 

1.573  0.625 

1.000 

1.833 

0.746 

1.434 

2.415 

1 . 

3740 

2235 

0.316 

0.909 

1.438  0.564 

0.968 

1.790 

0.646 

1.328 

2.296 

2..  .... 

3120 

1770 

0.260 

0.843 

1.367  0.546 

0.958 

1.775 

0.605 

1.276 

2.240 

3 . 

2480 

1405 

0.199 

0.763 

1.2780.507 

0.937 

1.747 

0.545 

1.208 

2.164 

4 . 

1960 

1115 

0.164 

0.698 

1.1990.449 

0.906 

1.704 

0.478 

1.143 

2.083 

5 . 

1560 

885 

0.135 

0.660 

1.146 

0.430 

0.896 

1.690 

0.451 

1.113 

2.042 

6 . 

1240 

700 

0.112 

0.627 

1.118 

0.410 

0.885 

1.675 

0.425 

1.084 

2.014 

45 


REINFORCED  CONCRETE  POLES 


Inasmuch  as  the  ice  and  wind  loads  are  both  acting  under  maxi¬ 
mum  loading,  some  reasonable  combination  must  be  assumed. 
Since  the  surface  exposed  to  wind  pressure  is  the  diameter  of  the  ice- 
covered  wire,  if  no  ice  load  is  present  it  would  be  necessary  to  assume 
an  extremely  high  wind  velocity  to  obtain  a  maximum  load  equiva¬ 
lent  to  a  moderate  combined  load. 

In  Tables  15,16,  and  1 7 are  given  the  breaking  strengths,  and  the  loads 
per  lineal  foot  of  wire,  for  various  sizes  of  wire  and  conditions  of  loading. 


TABLE  18.— TELEPHONE  AND  TELEGRAPH  WIRES. 
HARD-DRAWN,  SOLID,  BARE  COPPER. 


Gaugs. 

Diam. 

1 

Area. 

Ultimate  Strength. 

Load  Per  lin. 
Foot.  Vertical. 

Load  Per  Lin. 
Ft.  Horizontal. 

Max.  Load  Per 
Lin.  Ft.  Plane 
OF  Resultant. 

Dead 

Dead  +  Ice 

O 

HH 

+ 

nd 

cd 

0) 

p 

j  8.0  lbs.  Wind 

8.0  lbs.  P.  Sq. 
Ft.,  on  Y  Ice 

8.0  lbs.  P.  Sq. 

Ft.,  on  f"  Ice 

Dead,  8  lbs. 

Wind 

Dead,  Y'  Ice, 

8  lbs.  Wind 

il 

0^ 

QX 

No.  8  B.  W.G . 

0.165 

0.0214 

1285 

0.082 

0.496 

0.936 

0.110 

0.777 

1.110 

0.137 

0.922 

1.452 

No.  9  B.  &  S . 

0.114 

0.0103 

620 

0.039 

0.421 

.845 

0.076 

0.743 

1.076 

0.085 

0.854 

1.386 

No  12  N  B  S . 

0.104 

0  033 

No  14  N.  B.  S . 

0.080 

0  019 

P.  R.  R.  (old.) . 

0.110 

0.0095 

570 

6.037 

0.416 

0.802 

0.073 

0.740 

1.073 

0.082 

0.849 

1.339 

The  transition  in  pole  capacity  from  a  telegraph  or  telephone  line 
to  a  power  transmission  line  is  not  necessarily  discernible;  in  fact, 
the  load  per  foot  of  line  may  be  greater  in  the  former  case.  In 
telephone  and  telegraph  practice  it  is  desirable  that  the  wire  spacing 
and  the  sag  in  the  wires  be  kept  as  small  as  possible.  This  require¬ 
ment  immediately  places  a  limit  upon  the  length  of  span,  since  the 
wires  require  support  at  frequent  intervals.  In  power  transmission, 
however,  the  length  of  span  may  be  much  greater,  as  it  is  not  neces¬ 
sary  to  place  the  wires  close  together  and  the  sags  may  be  increased. 
Economically  speaking,  the  span  should  be  as  great  as  the  proper 
spacing  of  wires  and  the  necessary  clearance  between  the  wires  and 
the  ground  will  permit.  Within  limits,  an  increase  in  the  span  length 
merely  adds  an  inappreciable  amount  of  wire,  requires  a  greater 
distance  between  the  wires,  a  slight  increase  in  the  pole  height,  and, 
sometimes,  a  better  grade  of  insulator.  On  the  other  hand,  both  the 
number  of  insulators  and  the  number  of  poles  is  reduced. 

While  it  is  common  practice  to  use  wire  guys,  in  open  country, 
both  normal  and  parallel  to  the  line,  in  populated  districts  the  use 

46 


UNIVERSAL  PORTLAND  CEMENT  CO. 


of  guys  is  necessarily  restricted,  and  in  any  case  constitutes  a  nuisance 
and  expense  in  maintenance. 

While  the  combination  of  a  high  wind  and  a  large  accretion  of 
ice  is  not  entirely  unknown,  such  combinations  are  not  very  frequent, 
occurring  perhaps  once  in  a  decade.  If  it  is  desired  to  reduce  the 
first  cost  as  much  as  is  compatible  with  safety,  the  poles  may  be 
designed,  using  high-unit  stresses  for  conditions  that  rarely,  if  ever, 
occur.  In  regard  to  the  factors  of  safety,  unit  stresses,  and  working 
stresses,  to  be  allowed  in  the  constituent  materials  of  a  reinforced 
concrete  pole,  there  is  as  much  room  for  latitude  of  judgment  as  in 
other  structural  work.  The  character  of  service  is  not  closely  akin 
to  that  of  bridges  or  buildings,  and  the  factors  of  safety  common  to 
such  work  would  be  somewhat  conservative,  for  poles  computed  for 
extreme  conditions  of  loading. 

The  present  practice  differs  rather  widely  as  to  the  most  econom¬ 
ical  or  most  desirable  distribution  of  reinforcement.  It  is  now  gener¬ 
ally  conceded,  in  reinforced  concrete  work,  that  the  finer  the  dis¬ 
tribution  of  metal,  the  greater  the  homogeneity  and  strength  of  the 
construction.  Hov/ever,  in  the  case  of  poles,  where  the  concrete  is 
deposited  within  narrow  forms,  other  conditions  partly  modify  or 
control  the  distribution.  If  the  metal  is  concentrated  in  four  equal 
areas,  a  rod  to  each  corner,  a  square  pole  will  be  equally  strong,  either 
parallel  or  normal  to  the  line.  Other  or  finer  distribution  of  metal 
with  equal  strength  in  both  directions  necessitates  an  excess  of  mate¬ 
rial  over  that  required  for  the  forces  normal  to  the  line.  When  the 
metal  is  concentrated,  the  fabrication  of  the  reinforcement  into  a 
unit  frame,  and  also  the  concreting  operations,  are  more  easily  ac¬ 
complished.  It  may  be  said,  as  in  the  case  of  beams,  that  ample 
web  reinforcement  assures  a  firm  unyielding  unit  during  concreting, 
as  well  as  provision  against  vertical  shearing  stresses. 

In  other  fields  of  reinforced  concrete  work  high-carbon  steel  with  a 
high  elastic  limit,  and  a  correspondingly  richer  concrete,  are  being 
used,  permitting  higher  working  stresses  in  design.  If,  in  such  work, 
high-unit  stresses  can  be  used,  with  a  large  percentage  for  impact, 
it  would  seem  entirely  reasonable  to  use  correspondingly  high  work¬ 
ing  stresses  in  pole  design,  since  the  severe  conditions  of  loading  occur 
infrequently. 

The  most  commonly  used  mixture  is  I  :  2  : 4  Portland  cement, 
sand,  and  broken  stone  or  gravel.  It  should  be  mixed  wet,  using 
carefully  selected  materials,  with  the  fine  aggregate  next  to  the 
forms,  and  tamped  or  churned  to  eliminate  air-bubbles.  Such  a 

47 


REINFORCED  CONCRETE  POLES 


mixture  has  an  average  compressive  strength  of  about  900  pounds 
per  square  inch  in  seven  days,  2400  pounds  per  square  inch  in  one 
month,  3100  pounds  per  square  inch  in  three  months  and  4400 
pounds  per  square  inch  in  six  months.  If  conditions  make  it 
•  desirable  to  use  high  working  stresses,  a  month  or  more  should 
elapse  before  new  poles  undergo  severe  tests. 

Since  in  solid  poles  of  light  capacity  the  loading  produces  a  low 
compressive  unit  stress  in  the  concrete,  a  considerable  area  of  con¬ 
crete  might  be  omitted,  or,  theoretically,  the  economical  section 
would  be  a  hollow  one. 

The  increased  weight  of  a  solid  pole  renders  it  more  difficult  to 
handle,  and  a  hollow  pole  would  therefore  be  more  economical  in 
erection.  Further,  the  sides  of  the  pole  resisting  the  bending  stress 
normal  to  the  line  might  be  at  a  greater  distance  from  the  center 
than  the  sides  perpendicular  to  the  line. 

There  are,  however,  certain  objections  to  the  use  of  hollow  or 
unsymmetrical  sections.  The  former  are  difficult  to  make  properly, 
and  the  cost  of  the  forms  is  greatly  in  excess  of  that  required  for 
solid  sections.  The  unsymmetrical  sections  may  perhaps  be  open  to 
criticism  on  the  score  of  appearance,  and  if  the  lack  of  symmetry  is 
very  pronounced,  render  the  poles  relatively  weak  in  the  direction  of 
the  line.  Conservative  reasoning  would  dictate  that  such  poles, 
sometimes  styled  ^^whip  lash’’  construction,  should  be  interspersed 
with  dead-end”  poles  of  heavier  design. 

In  general,  a  square,  octagonal,  circular  or  other  cross-section 
may  be  used,  but  it  is  desirable  as  a  matter  of  appearance,  since 
sharp  corners  are  difficult  to  make  and  subject  to  accident,  that  all 
such  corners  be  chamfered  or  rounded.  The  minimum  diameter,  or 
width,  at  the  top  may  be  made  6  inches  for  small  poles,  and  increased 
as  required  for  the  strength  and  appearance  of  long  poles  or  poles 
carrying  a  heavy  line.  In  any  case  care  should  be  exercised,  in 
determining  the  taper  and  reinforcement,  that  no  weak  section  occurs 
at  some  distance  above  the  ground-level. 

As  a  study  of  the  size  and  appearance  of  reinforced  concrete  poles 
of  different  strengths,  and  to  illustrate  the  relative  line  capacities 
represented  by  the  various  loadings  given  in  the  preceding  experi¬ 
ments,  a  number  of  designs  were  made,  which  are  shown  in  Figs.  32, 
32a,  33,  33a,  34,  and  34a.  Three  different  line  capacities  were 
assumed  and  two  designs  made  for  each,  in  order  to  show  the  in¬ 
fluence  of  high-unit  stresses  on  the  appearance,  weight,  and  cost  of 
the  poles. 


48 


UNIVERSAL  PORTLAND  CEMENT  CO. 


Fig.  32. 
49 


REINFORCED  CONCRETE  POLES 


The  poles  shown  in  Fig.  32  were  designed  for  150-foot  spans, 
those  in  Figs.  33  and  33a  for  120-foot  spans,  and  those  in  Figs.  34 
and  34a,  for  100-foot  spans. 

All  the  poles  were  designed  for  the  same  elemental  loads,  i.  e., 
Y2  inch  of  ice  and  8.0  pounds  per  square  foot  wind  pressure  thereon, 
and  13.0  pounds  per  square  foot  wind  pressure  on  the  pole;  and  the 
loads  equivalent  to  Y2  inch  of  ice  and  2.0  pounds  wind  pressure  have 
been  shown  on  Figs.  32a,  33a,  and  34a  merely  for  comparison. 

The  unit  stresses,  quantities,  etc.,  are  given  in  Table  19,  page  56. 

The  web  system,  not  shown  in  the  illustrations,  consists  in  a 
spiral  of  No.  12  wire  placed  outside  the  rods  and  securely  attached 
to  them,  and  in  horizontal  ties  1"  wide  X  Y%  'to  }/Y  thick,  3  to 
5  ft.  apart,  depending  upon  the  particular  design.  The  reinforce¬ 
ment  thus  forms  an  independent  skeleton,  which  can  be  assembled, 
handled,  and  lowered  into  the  forms. 

The  poles  were  designed  to  withstand  the  total  force  perpendicular 
to  the  direction  of  the  line,  and  good  practice  apparently  justifies  an 
equal,  or  nearly  equal,  strength  parallel  to  the  line. 

The  linear  variation  of  stress,  and  the  usual  methods  of  computing 
beams  doubly  reinforced,  were  used. 

The  reinforcing  rods  were  assumed  to  be  of  a  mechanical  bond 
type,  particularly  in  the  designs  with  high-tension  steel,  although  the 
frequent  attachment  of  the  web  system  would  doubtless  be  of  assis¬ 
tance  in  developing  the  necessary  bond. 

The  extreme  fiber  stress  in  concrete  in  compression  in  these  de¬ 
signs  is  about  the  one-month  value  of  the  crushing  strength  of  con¬ 
crete,  and  it  is  more  than  probable  that  such  poles  will  have  attained 
a  greater  age  before  they  would  be  tested  under  the  actual  conditions 
for  which  they  were  figured. 


50 


UNIVERSAL  PORTLAND  CEMENT  CO. 


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REINFORCED  CONCRETE  POLES 


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55 


TABLE  19.— UNIT  STRESSES  AND  QUANTITIES. 


REINFORCED  CONCRETE  POLES 


6 

z 

M 

P5 

m 

w 


Lrc. 

Ties. 

1 

1 

47 

o 

lO  lO 

lO  o 

CO 

65 

hi 

o 

o  o 

O  O 

o 

H  aj 

Ph 

m 

00  o 

CO  (M 

CO 

(M 

(N  CO 

<M  CO 

CO 

Wt. 

Steel 

Rods. 

660 

540 

550 

493 

632 

300 

Cu.  Ft. 
Con¬ 
crete. 

23.0 

28.0 

19.0 

10.0 

39.0 

25.0 

Ext. 

Fibre 

Stress 

Con¬ 

crete. 

1960  " 

1470  " 
1100  " 

2400  " 

1840  " 

1130  " 

%  Ten¬ 
sion 
Steel 

G.  L. 

2.40% 

1.44% 

2.04% 

3.22% 

2.20% 

1.64% 

Gross  % 
Steel 

G.  L. 

5.60% 

3.38% 

5.25% 

3.33% 

4.95% 

4.12% 

Unit 

Comp. 

Stress 

Steel. 

19100  " 

1 

20800  " 
12000  " 

21700  " 
18000  " 

1 

12000  " 

Unit 

Ten. 

Stress 

S. 

40000  " 

25000  " 
24000  '' 

40500  " 
40000  " 

25500  " 

Req’d  a. 

FOR 

Steel. 

d  -  -  -  -  - 

cr  h.  h,  .... 

(JQ  ..  h,  h.  h, 

00  (M  Ttl  lO  00  (M 

CO  (M  !>•.  CO 

CO  (Oi  oi  (oi  c4  CO 

Edge 

Dist. 

FOR 

Steel. 

1.75  in, 

1.50  in. 
1.25  in. 

1.25  in. 

1.50  in. 

1.50  in. 

Span 

lOO'-O" 

do  do 
150'-0" 

1 

1 

do  do 
120'-0" 

do  do 

Width 

AT 

Ground 

L. 

12.6  in 

14.5  in 
12.0  in 

9.0  in 
12.0  in 

i 

15.0  in 

Total 

Bal. 

Foot 

Lbs. 

(22400) 

89460 

89460 

(12570) 

49450 

49450 

21000 

84034 

94034 

Pole. 

Trunk  . 

Do 

Light 

30  ft. 
Do 

Medium 
35  ft. 
Do 

C<1 


56 


UNIVERSAL  PORTLAND  CEMENT  CO. 


57 


•4-  RODS  SS 


REINFORCED  CONCRETE  POLES 


Fig.  36. — Hennebique  pole  design. 
58 


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REINFORCED  CONCRETE  POLES 

CONCRETE  PAVEMENTS,  Their  Cost  and  Construction,  witli  Specifications 

PORTLAND  CEMENT  SIDEWALK  CONSTRUCTION 

STANDARD  SPECIFICATIONS  AND  UNIFORM  METHODS  OF 
TESTING  AND  ANALYSIS  FOR  PORTLAND  CEMENT 

CONCRETE  IN  THE  COUNTRY 

MONTHLY  BULLETIN 

FARM  CEMENT  NEWS,  A  Periodical  on  the  Use  of  Cement  for  the 
Progressive  Farmer. 

No.  3  -“Selecting  and  Mixing  Materials  for  Concrete” 

No.  4 — “Concrete  Walks  and  Floors” 

No.  5 — “Concrete  Foundations” 

No.  6 — “Concrete  Troughs  and  Tanks” 

No.  7 — “Concrete  Line  Fence  Posts” 

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No.  9-  “Concrete  Building  Blocks” 

No.  10 — “Concrete  Walls” 


Write  to  the  nearest  office  of  the 

Universal  Portland  Cement  Co. 


CHICAGO 
72  West  Adams  St. 


PITTSBURG 
F rick  Building 


MINNEAPOLIS 
Security  Bank  Bldg. 


} 


Regularity  in  the  setting  prop¬ 
erties  of  Portland  Cement  in- 
the  user  freedom  from  the 
peiplexities  which  mark 
the  use  of  uncertain  and  question¬ 
able  brands.  Universal’s  record 
of  eleven  years  of  satisfactory 
use  in  every  form  of  concrete 
construction  in  strikingly  increas¬ 
ing  quantities  is  significant  evi¬ 
dence  of  its  uniform  high  quality. 


sures 


Omyersal  Portland  Cement 

/  ^--—  Chicago — Pittsburg 


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